Variable magnification optical system, optical apparatus, and method for manufacturing variable magnification optical system

ABSTRACT

A variable magnification optical system includes, in order from an object: a first lens group (G1) having a negative refractive power; a second lens group (G2); a third lens group (G3); a fourth lens group (G4) having a negative refractive power; and a fifth lens group (G5) having a positive refractive power, the system performing varying magnification by changing the distance between the first and second lens groups, the distance between the second and third lens groups, the distance between the third and fourth lens groups, and the distance between the fourth and fifth lens groups, and the fourth lens group including a 42nd lens group (G42) configured to be movable so as to have a component in a direction orthogonal to an optical axis and a 41st lens group (G41) disposed at an object-side of the 42nd lens group.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical apparatus, and a method for manufacturing thevariable magnification optical system.

TECHNICAL BACKGROUND

Conventionally, a variable magnification optical system having a wideangle of view including a camera shake compensation mechanism has beenproposed (for example, see Patent Documents 1 and 2).

RELATED ART DOCUMENTS Patent Document

-   Patent Document 1:

Japanese Patent Application, Publication No. 2014-160229

-   Patent Document 2:

Japanese Patent Application, Publication No. H11-231220

SUMMARY OF INVENTION Technical Problem

In recent years, there has been an increasing demand for a variablemagnification optical system which has a satisfactory opticalperformance and a wide angle of view or a small F-value.

Solution to Problem

According to an aspect of the present invention, there is provided avariable magnification optical system including, in order from anobject: a first lens group having a negative refractive power; a secondlens group; a third lens group; a fourth lens group having a negativerefractive power; and a fifth lens group having a positive refractivepower, wherein the system performs varying magnification by changing thedistance between the first lens group and the second lens group, thedistance between the second lens group and the third lens group, thedistance between the third lens group and the fourth lens group, and thedistance between the fourth lens group and the fifth lens group, and thefourth lens group includes a 42nd lens group configured to be movable soas to have a component in a direction orthogonal to an optical axis anda 41st lens group disposed at an object-side of the 42nd lens group.

According to another aspect of the present invention, there is provideda variable magnification optical system including, in order from anobject: a first lens group having a negative refractive power; a secondlens group having a positive refractive power; a third lens group havinga positive refractive power; a fourth lens group having a negativerefractive power; and a fifth lens group having a positive refractivepower, the system performing varying magnification by changing thedistances between the respective lens groups, the fourth lens groupincluding a 42nd lens group configured to be movable so as to have acomponent in a direction orthogonal to an optical axis and a 41st lensgroup which is disposed at an object-side of the 42nd lens group and ofwhich the position in the direction orthogonal to the optical axisduring image blur correction is immovable.

According to another aspect of the present invention, there is providedan optical apparatus having the above-described variable magnificationoptical system mounted thereon.

According to another aspect of the present invention, there is provideda method for manufacturing a variable magnification optical system,wherein the variable magnification optical system includes, in orderfrom an object: a first lens group having a negative refractive power; asecond lens group; a third lens group; a fourth lens group having anegative refractive power; and a fifth lens group having a positiverefractive power, the system performing varying magnification bychanging the distance between the first lens group and the second lensgroup, the distance between the second lens group and the third lensgroup, the distance between the third lens group and the fourth lensgroup, and the distance between the fourth lens group and the fifth lensgroup, and wherein the method includes: arranging the respective lensesin a lens barrel such that the fourth lens group includes a 42nd lensgroup configured to be movable so as to have a component in a directionorthogonal to an optical axis and a 41st lens group disposed at anobject-side of the 42nd lens group.

According to another aspect of the present invention, there is provideda method for manufacturing a variable magnification optical system,wherein the variable magnification optical system includes, in orderfrom an object: a first lens group having a negative refractive power; asecond lens group having a positive refractive power; a third lens grouphaving a positive refractive power; a fourth lens group having anegative refractive power; and a fifth lens group having a positiverefractive power, the system performing varying magnification bychanging the distances between the respective lens groups, and whereinthe method includes: arranging the respective lenses in a lens barrelsuch that the fourth lens group includes a 42nd lens group configured tobe movable so as to have a component in a direction orthogonal to anoptical axis and a 41st lens group which is disposed at an object-sideof the 42nd lens group and of which the position in the directionorthogonal to the optical axis during image blur correction isimmovable.

According to another aspect of the present invention, there is provideda variable magnification optical system including, in order from anobject: a first lens group having a negative refractive power; a secondlens group having a positive refractive power; a third lens group; afourth lens group; and a fifth lens group having a positive refractivepower, wherein the system performs varying magnification by changing thedistance between the first lens group and the second lens group, thedistance between the second lens group and the third lens group, thedistance between the third lens group and the fourth lens group, and thedistance between the fourth lens group and the fifth lens group, atleast a portion of the fourth lens group is configured to be movable soas to have a component in a direction orthogonal to an optical axis, andthe system satisfies the following conditional expressions.−0.400<(D34T−D34W)/(D23T−D23W)<1.000−0.400<f4/f3<0.450

where

D34T: an air distance between the third and fourth lens groups in atelephoto end state

D34W: an air distance between the third and fourth lens groups in awide-angle end state

D23T: an air distance between the second and third lens groups in atelephoto end state

D23W: an air distance between the second and third lens groups in awide-angle end state

f4: a focal length of the fourth lens group

f3: a focal length of the third lens group

According to another aspect of the present invention, there is provideda variable magnification optical system including, in order from anobject: a first lens group having a negative refractive power; a secondlens group having a positive refractive power; a third lens group; afourth lens group having a negative refractive power; and a fifth lensgroup having a positive refractive power, the system performing varyingmagnification by changing the distances between the respective lensgroups, wherein at least a portion of the fourth lens group isconfigured to be movable so as to have a component in a directionorthogonal to an optical axis, and the system satisfies the followingconditional expressions.−0.400<(D34T−D34W)/(D23T−D23W)<1.000−0.400<f4/f3<0.450

where

D34T: an air distance between the third and fourth lens groups in atelephoto end state

D34W: an air distance between the third and fourth lens groups in awide-angle end state

D23T: an air distance between the second and third lens groups in atelephoto end state

D23W: an air distance between the second and third lens groups in awide-angle end state

f4: a focal length of the fourth lens group

f3: a focal length of the third lens group

According to another aspect of the present invention, there is providedan optical apparatus having the above-described variable magnificationoptical system mounted thereon.

According to another aspect of the present invention, there is provideda method for manufacturing a variable magnification optical system,wherein the variable magnification optical system includes, in orderfrom an object: a first lens group having a negative refractive power; asecond lens group having a positive refractive power; a third lensgroup; a fourth lens group; and a fifth lens group having a positiverefractive power, the system performing varying magnification bychanging the distance between the first lens group and the second lensgroup, the distance between the second lens group and the third lensgroup, the distance between the third lens group and the fourth lensgroup, and the distance between the fourth lens group and the fifth lensgroup, wherein at least a portion of the fourth lens group is configuredto be movable so as to have a component in a direction orthogonal to anoptical axis, and wherein the method includes: arranging the respectivelenses in a lens barrel so as to satisfy the following conditionalexpressions.−0.400<(D34T−D34W)/(D23T−D23W)<1.000−0.400<f4/f3<0.450

where

D34T: an air distance between the third and fourth lens groups in atelephoto end state

D34W: an air distance between the third and fourth lens groups in awide-angle end state

D23T: an air distance between the second and third lens groups in atelephoto end state

D23W: an air distance between the second and third lens groups in awide-angle end state

f4: a focal length of the fourth lens group

f3: a focal length of the third lens group

According to another aspect of the present invention, there is provideda method for manufacturing a variable magnification optical system,wherein the variable magnification optical system includes, in orderfrom an object: a first lens group having a negative refractive power; asecond lens group having a positive refractive power; a third lensgroup; a fourth lens group having a negative refractive power; and afifth lens group having a positive refractive power, the systemperforming varying magnification by changing the distances between therespective lens groups, wherein at least a portion of the fourth lensgroup is configured to be movable so as to have a component in adirection orthogonal to an optical axis, and wherein the methodincludes: arranging the respective lenses in a lens barrel so as tosatisfy the following conditional expressions.−0.400<(D34T−D34W)/(D23T−D23W)<1.000−0.400<f4/f3<0.450

where

D34T: an air distance between the third and fourth lens groups in atelephoto end state

D34W: an air distance between the third and fourth lens groups in awide-angle end state

D23T: an air distance between the second and third lens groups in atelephoto end state

D23W: an air distance between the second and third lens groups in awide-angle end state

f4: a focal length of the fourth lens group

f3: a focal length of the third lens group

According to another aspect of the present invention, there is provideda variable magnification optical system including, in order from anobject: a first lens group having a negative refractive power; a secondlens group having a positive refractive power; a third lens group havinga positive refractive power; a fourth lens group; a fifth lens grouphaving a negative refractive power; and a sixth lens group having apositive refractive power, wherein the system performs varyingmagnification by changing the distance between the first lens group andthe second lens group, the distance between the second lens group andthe third lens group, the distance between the third lens group and thefourth lens group, the distance between the fourth lens group and thefifth lens group, and the distance between the fifth lens group and thesixth lens group, and at least a portion of any one lens group among thefirst to sixth lens groups is configured to be movable so as to have acomponent in a direction orthogonal to an optical axis.

According to another aspect of the present invention, there is provideda variable magnification optical system including, in order from anobject: a first lens group having a negative refractive power; a secondlens group having a positive refractive power; a third lens group havinga positive refractive power; a fourth lens group; a fifth lens grouphaving a negative refractive power; and a sixth lens group having apositive refractive power, the system performing varying magnificationby changing the distances between the respective lens groups, wherein atleast a portion of any one lens group among the first to sixth lensgroups is configured to be movable so as to have a component in adirection orthogonal to an optical axis.

According to another aspect of the present invention, there is providedan optical apparatus having the above-described variable magnificationoptical system mounted thereon.

According to another aspect of the present invention, there is provideda method for manufacturing a variable magnification optical system,wherein the variable magnification optical system includes, in orderfrom an object: a first lens group having a negative refractive power; asecond lens group having a positive refractive power; a third lens grouphaving a positive refractive power; a fourth lens group; a fifth lensgroup having a negative refractive power; and a sixth lens group havinga positive refractive power, the system performing varying magnificationby changing the distance between the first lens group and the secondlens group, the distance between the second lens group and the thirdlens group, the distance between the third lens group and the fourthlens group, the distance between the fourth lens group and the fifthlens group, and the distance between the fifth lens group and the sixthlens group, and wherein the method includes: arranging the respectivelenses in a lens barrel such that at least a portion of any one lensgroup among the first to sixth lens groups is configured to be movableso as to have a component in a direction orthogonal to an optical axis.

According to another aspect of the present invention, there is provideda method for manufacturing a variable magnification optical system,wherein the variable magnification optical system includes, in orderfrom an object: a first lens group having a negative refractive power; asecond lens group having a positive refractive power; a third lens grouphaving a positive refractive power; a fourth lens group; a fifth lensgroup having a negative refractive power; and a sixth lens group havinga positive refractive power, the system performing varying magnificationby changing the distances between the respective lens groups, andwherein arranging the respective lenses in a lens barrel such that atleast a portion of any one lens group among the first to sixth lensgroups is configured to be movable so as to have a component in adirection orthogonal to an optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a variable magnification opticalsystem according to Example 1, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 2 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 1 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 3 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 1 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 4 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 1 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 5 is a cross-sectional view of a variable magnification opticalsystem according to Example 2, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 6 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 2 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 7 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 2 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 8 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 2 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 9 is a cross-sectional view of a variable magnification opticalsystem according to Example 3, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 10 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 3 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 11 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 3 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 12 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 3 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 13 is a cross-sectional views of a variable magnification opticalsystem according to Example 4, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 14 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 4 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 15 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 4 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 16 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 4 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 17 is a cross-sectional view of a variable magnification opticalsystem according to Example 5, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 18 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 5 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 19 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 5 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 20 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 5 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 21 is a cross-sectional view of a variable magnification opticalsystem according to Example 6, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 22 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 6 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 23 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 6 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 24 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 6 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 25 is a cross-sectional view of a variable magnification opticalsystem according to Example 7, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 26 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 7 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 27 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 7 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 28 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 7 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 29 is a cross-sectional view of a variable magnification opticalsystem according to Example 8, wherein parts (W), (M), and (T) are in awide-angle end state, an intermediate focal length state, and atelephoto end state, respectively.

FIG. 30 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 8 upon focusing on anobject at infinity, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 31 shows graphs illustrating various aberrations of the variablemagnification optical system according to Example 8 upon focusing on anobject at a close point, wherein parts (a), (b), and (c) are in thewide-angle end state, the intermediate focal length state, and thetelephoto end state, respectively.

FIG. 32 shows graphs illustrating lateral aberrations of the variablemagnification optical system according to Example 8 after image blurcorrection was performed upon focusing on an object at infinity, whereinparts (a), (b), and (c) are in the wide-angle end state, theintermediate focal length state, and the telephoto end state,respectively.

FIG. 33 is a diagram illustrating an example of a configuration of acamera having a variable magnification optical system mounted thereon.

FIG. 34 is a diagram illustrating an outline of an example of a methodfor manufacturing a variable magnification optical system.

FIG. 35 is a diagram illustrating an outline of an example of a methodfor manufacturing a variable magnification optical system.

FIG. 36 is a diagram illustrating an outline of another example of amethod for manufacturing a variable magnification optical system.

FIG. 37 is a diagram illustrating an outline of another example of amethod for manufacturing a variable magnification optical system.

FIG. 38 is a diagram illustrating an outline of another example of amethod for manufacturing a variable magnification optical system.

FIG. 39 is a diagram illustrating an outline of another example of amethod for manufacturing a variable magnification optical system.

DESCRIPTION OF EMBODIMENTS

An embodiment will now be described with reference to the drawings. FIG.1 illustrates an example of a configuration of a variable magnificationoptical system (variable power optical system) ZL. In other examples,the number of lens groups, a lens configuration of each lens group, andthe like can be changed appropriately.

In an embodiment, a variable magnification optical system ZL includes,in order from an object, a first lens group G1 having a negativerefractive power; a second lens group G2; a third lens group G3; afourth lens group G4 having a negative refractive power; and a fifthlens group G5 having a positive refractive power, the system performingvarying magnification (varying power) by changing the distance betweenthe first and second lens groups G1 and G2, the distance between thesecond and third lens groups G2 and G3, the distance between the thirdand fourth lens groups G3 and G4, and the distance between the fourthand fifth lens groups G4 and G5, wherein the fourth lens group G4includes a 42nd lens group G42 configured to be movable so as to have acomponent in the direction orthogonal to the optical axis and a 41stlens group G41 disposed at an object-side of the 42nd lens group G42. Inan example, at least one of the second lens group G2 and the third lensgroup G3 has a positive refractive power.

Alternatively, a variable magnification optical system ZL includes, inorder from an object, a first lens group G1 having a negative refractivepower, a second lens group G2 having a positive refractive power, athird lens group G3 having a positive refractive power, a fourth lensgroup G4 having a negative refractive power, and a fifth lens group G5having a positive refractive power, the system performing varyingmagnification by changing the distances between the respective lensgroups, wherein the fourth lens group G4 includes a 42nd lens group G42configured to be movable so as to have a component in the directionorthogonal to the optical axis in order to correct image blur as avibration-reduction lens group VR and a 41st lens group G41 which isdisposed at an object-side of the 42nd lens group G42 and of which theposition in the direction orthogonal to the optical axis during imageblur correction is immovable.

As described above, the variable magnification optical system has lensgroups having negative, positive, positive, negative, and positiverefractive powers and changes the distances between the respective lensgroups. Therefore, it is possible to implement a variable magnificationoptical system having a wide angle of view. Moreover, the fourth lensgroup G4 is configured to have, in order from the object, the 41st lensgroup G41 and the 42nd lens group G42, and the 42nd lens group G42 ismoved so as to have a component in the direction orthogonal to theoptical axis to perform image blur correction. Therefore, it is possibleto suppress the occurrence of eccentric coma aberration and one-sidedblur during image blur correction and to obtain satisfactory imagingperformance.

The 41st lens group G41 may have a positive refractive power or anegative refractive power.

The fourth lens group G4 may have one or more lenses (which areimmovable during image blur correction) at an image-side of the 42ndlens group G42.

In the variable magnification optical system ZL, it is preferable thatthe 42nd lens group G42 have a negative refractive power.

When the 42nd lens group G42 has a negative refractive power, it ispossible to correct tilting (one-sided blur) of the image plane and theoccurrence of eccentric aberration (particularly eccentric comaaberration) satisfactorily when the 42nd lens group G42 is moved so asto have the component in the direction orthogonal to the optical axis inorder to correct image blur.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (1) below.0.700<f42/f4<1.700  (1)

where

f42: a focal length of the 42nd lens group G42

f4: a focal length of the fourth lens group G4

Conditional Expression (1) is a conditional expression for defining thefocal length of the 42nd lens group G42 which is a vibration-reductionlens group VR with respect to the focal length of the fourth lens groupG4. When Conditional Expression (1) is satisfied, it is possible tocontrol a moving distance of the 42nd lens group G42 moved during imageblur correction appropriately while obtaining satisfactory imagingperformance during image blur correction.

When the focal length ratio exceeds the upper limit value of ConditionalExpression (1), the focal length of the 42nd lens group G42 is increasedand the moving distance of the 42nd lens group G42 during image blurcorrection becomes too large. Due to this, the size of an image blurcorrection mechanism may increase.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (1) be set to 1.600. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (1) be set to 1.500.

When the focal length ratio is smaller than the lower limit value ofConditional Expression (1), the focal length of the 42nd lens group G42is decreased, the occurrence of one-sided blur or eccentric comaaberration occurring during image blur correction increases, and it isdifficult to maintain satisfactory imaging performance during image blurcorrection.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (1) be set to 0.800. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (1) be set to 0.900.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (2) below.−0.400<f4/f41<0.500  (2)

where

f4: a focal length of the fourth lens group G4

f41: a focal length of the 41st lens group G41

Conditional Expression (2) is a conditional expression for defining thefocal length of the 41st lens group G41 with respect to the focal lengthof the fourth lens group G4. When Conditional Expression (2) issatisfied, it is possible to control a moving distance of the 42nd lensgroup G42 moved during image blur correction appropriately whileobtaining satisfactory imaging performance during image blur correction.

When the focal length ratio exceeds the upper limit value of ConditionalExpression (2), the negative refractive power of the 41st lens group G42is increased and the refractive power of the 42nd lens group G42 isweakened relatively. As a result, the moving distance of the 42nd lensgroup G42 during image blur correction becomes too large and the size ofthe image blur correction mechanism increases.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (2) be set to 0.400. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (2) be set to 0.300.

When the focal length ratio is smaller than the lower limit value ofConditional Expression (2), the positive refractive power of the 41stlens group G41 is increased and the negative refractive power of the42nd lens group G42 is strengthened relatively. As a result, theoccurrence of one-sided blur or eccentric coma aberration occurringduring image blur correction increases and it is not possible tomaintain satisfactory imaging performance during image blur correction.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (2) be set to −0.300. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (2) be set to −0.200.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (3) below.0.200<f1/f4<0.900  (3)

where

f1: a focal length of the first lens group G1

f4: a focal length of the fourth lens group G4

Conditional Expression (3) is a conditional expression forsatisfactorily correcting curvature of field and coma aberration whileobtaining a wide angle of view (a half-angle of view of approximately50° or more) in the wide-angle end state.

If the focal length ratio exceeds the upper limit value of ConditionalExpression (3), the focal length of the first lens group G1 is increasedand it is difficult to obtain a wide angle of view (a half-angle of viewof approximately 50° or more) in the wide-angle end state. In somecases, a total length and a lens diameter of the first lens group G1 areincreased undesirably.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (3) be set to 0.750. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (3) be set to 0.600.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (3), the focal length of the first lens group G1is decreased and it is difficult to correct curvature of field and comaaberration and to obtain satisfactory imaging performance.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (3) be set to 0.300. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (3) be set to 0.350.

In the variable magnification optical system ZL, it is preferable thatthe 41st lens group G41 have a negative lens and a positive lens.

According to this configuration, it is possible to correct one-sidedblur and eccentric coma aberration when the 42nd lens group G42 is movedto perform image blur correction and to secure imaging performance uponvarying magnification (particularly, it is possible to suppressfluctuation of spherical aberration, coma aberration, and astigmatism).

In the variable magnification optical system ZL, it is preferable thatthe 42nd lens group G42 be constituted by a cemented lens including apositive lens and a negative lens.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the 42nd lens groupG42 is moved to perform image blur correction. Moreover, it is possibleto decrease the size and the weight of a lens that moves for image blurcorrection and to effectively decrease the size of an image blurcorrection mechanism and the entire lens system.

The 42nd lens group G42 may include two lenses (separated from a bondingsurface) instead of bonding a positive lens and a negative lens asdescribed above.

In the variable magnification optical system ZL, it is preferable thatthe lens surface closest to an image, of the 42nd lens group G42 be anaspherical surface.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the 42nd lens groupG42 is moved to perform image blur correction.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (4) below.1.100<A(T3.5)/A(T4.0)<5.000  (4)

where

A(T3.5): an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 3.5 passes through the aspherical surface ina telephoto end state

A(T4.0): an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 4.0 passes through the aspherical surface ina telephoto end state

The asphericity refers to an amount of sag, with respect to anapproximately spherical surface, in the aspherical surface along theoptical axis.

Conditional Expression (4) is a Conditional Expression for defining anappropriate value of the asphericity of the aspherical surface closestto an image, of the 42nd lens group G42. When Conditional Expression (4)is satisfied, it is possible to satisfactorily correct one-sided blurand eccentric coma aberration when the 42nd lens group G42 is moved toperform image blur correction.

When the asphericity ratio exceeds the upper limit value of ConditionalExpression (4), the asphericity of the 42nd lens group G42 becomes toolarge and it is difficult to correct one-sided blur and eccentric comaaberration when the 42nd lens group G42 is moved to perform image blurcorrection.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (4) be set to 4.000. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (4) be set to 3.000.

When the asphericity ratio is smaller than the lower limit value ofConditional Expression (4), the asphericity of the 42nd lens group G42is insufficient and it is difficult to correct one-sided blur andeccentric coma aberration when the 42nd lens group G42 is moved toperform image blur correction.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (4) be set to 1.250. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (4) be set to 1.400.

In the variable magnification optical system ZL, it is preferable thatthe first lens group G1 be immovable in relation to the image plane uponvarying magnification, for example.

According to this configuration, it is possible to effectively simplifya varying magnification mechanism and to increase the durability of alens barrel.

In the variable magnification optical system ZL, it is preferable thatfocusing be performed by moving the second lens group G2 in the opticalaxis direction as a focusing lens group.

According to this configuration, it is possible to decrease the size andthe weight of a focusing lens group and to decrease the size of anentire lens system and to increase a focusing speed during autofocus.

In this way, it is possible to implement the variable magnificationoptical system ZL which has a wide angle of view and in which variousaberrations are corrected satisfactorily.

Next, a camera (an optical apparatus) having the above-describedvariable magnification optical system ZL will be described withreference to the drawings. FIG. 33 illustrates an example of aconfiguration of a camera having a variable magnification optical systemmounted thereon.

As illustrated in FIG. 33 , a camera 1 is an interchangeable lens camera(a so-called mirrorless camera) having the above-described variablemagnification optical system ZL as an image capturing lens 2. In thiscamera, light from an object (a subject) which is not illustrated iscollected by the image capturing lens 2 and forms a subject image on animage plane of the imaging unit 3 via an optical low-pass filter (OLPF)which is not illustrated. The subject image is photoelectricallyconverted by a photoelectric conversion element provided in the imagingunit 3, whereby the image of the subject is generated. This image isdisplayed on an electronic view finder (EVF) 4 provided in the camera 1.In this way, a photographer can observe the subject via the EVF 4.Moreover, when a release button (not illustrated) is pressed by thephotographer, the image of the subject generated by the imaging unit 3is stored in a memory (not illustrated). In this way, the photographercan capture an image of the subject using the camera 1.

As can be understood from respective examples to be described later, thevariable magnification optical system ZL mounted on the camera 1 as theimage capturing lens 2 has a wide angle of view and has a satisfactoryoptical performance such that various aberrations are correctedsatisfactorily due to its characteristic lens configuration. Therefore,according to the camera 1, it is possible to implement an opticalapparatus which has a wide angle of view and has a satisfactory opticalperformance such that various aberrations are corrected satisfactorily.

Although a mirrorless camera has been described as an example of thecamera 1, the camera is not limited to this. For example, the sameeffect as the camera 1 can be obtained even when the above-describedvariable magnification optical system ZL is mounted on a single-lensreflex camera which has a quick return mirror on a camera body and viewsa subject using a finder optical system.

Next, an example of a method for manufacturing the above-describedvariable magnification optical system ZL will be described. FIGS. 34 and35 illustrate an example of a method for manufacturing the variablemagnification optical system ZL.

In the example illustrated in FIG. 34 , first, respective lensesincluding a first lens group G1 having a negative refractive power; asecond lens group G2; a third lens group G3; a fourth lens group G4having a negative refractive power; and a fifth lens group G5 having apositive refractive power are arranged, in order from an object, in alens barrel such that varying magnification is performed by changing thedistance between the first and second lens groups G1 and G2, thedistance between the second and third lens groups G2 and G3, thedistance between the third and fourth lens groups G3 and G4, and thedistance between the fourth and fifth lens groups G4 and G5 (step ST1).The respective lenses are arranged such that the fourth lens group G4includes a 42nd lens group G42 configured to be movable so as to have acomponent in the direction orthogonal to the optical axis and a 41stlens group G41 disposed at an object-side of the 42nd lens group G42(step ST2).

In the example illustrated in FIG. 35 , first, respective lensesincluding a first lens group G1 having a negative refractive power, asecond lens group G2 having a positive refractive power, a third lensgroup G3 having a positive refractive power, a fourth lens group G4having a negative refractive power, and a fifth lens group G5 having apositive refractive power are arranged, in order from an object, in alens barrel, the system performing varying magnification by changing thedistances between the respective lens groups (step ST10). The respectivelenses are arranged such that the fourth lens group G4 includes a 42ndlens group G42 configured to be movable so as to have a component in thedirection orthogonal to the optical axis in order to correct image blurand a 41st lens group G41 which is disposed at an object-side of the42nd lens group G42 and of which the position in the directionorthogonal to the optical axis during image blur correction is immovable(step ST20).

According to an example of a lens arrangement, as illustrated in FIG. 1, a negative meniscus lens L11 having a concave surface oriented towardan image side, a biconcave lens L12, a biconcave lens L13, and abiconvex lens L14 are arranged, in order from the object, to form thefirst lens group G1. A biconvex lens L21 and a cemented lens including anegative meniscus lens L22 having a concave surface oriented toward theimage side and a positive meniscus lens L23 having a convex surfaceoriented toward the object side are arranged, in order from the object,to form the second lens group G2. A cemented lens including a biconvexlens L31 and a negative meniscus lens L32 having a concave surfaceoriented toward the object side arranged, in order from the object,forms the third lens group G3. A biconcave lens L41, a biconvex lensL42, and a cemented lens including a biconcave lens L43 and a positivemeniscus lens L44 having a convex surface oriented toward the objectside are arranged, in order from the object, to form the fourth lensgroup G4. A biconvex lens L51, a cemented lens including a biconvex lensL52 and a biconcave lens L53, and a cemented lens including a biconvexlens L54 and a biconcave lens L55 are arranged, in order from theobject, to form the fifth lens group G5. Moreover, in the fourth lensgroup G4, the lenses ranging from the biconcave lens L41 to the biconvexlens L42 form the 41st lens group G41 and the cemented lens includingthe biconcave lens L43 and the positive meniscus lens L44 having theconvex surface oriented toward the object side forms the 42nd lens groupG42 (the vibration-reduction lens group (VR)). The respective lensgroups prepared in this manner are arranged in the above-described orderto manufacture the variable magnification optical system ZL.

According to the above-described manufacturing method, it is possible tomanufacture the variable magnification optical system ZL which has awide angle of view and in which various aberrations are correctedsatisfactorily.

Hereinafter, respective examples will be described with reference to thedrawings.

FIGS. 1 and 5 are cross-sectional views illustrating the configurationand the refractive power allocation of variable magnification opticalsystems ZL (ZL1 to ZL2) according to respective examples. In the lowerpart of the cross-sectional views of the variable magnification opticalsystems ZL1 to ZL2, the moving directions along the optical axis of eachlens group upon varying magnification from the wide-angle end state (W)to the telephoto end state (T) via the intermediate focal length state(M) are indicated by arrows. In the upper part of the cross-sectionalviews of the variable magnification optical systems ZL1 to ZL2, themoving direction of the focusing lens group upon focusing from an objectat infinity to an object at a close distance is indicated by an arrowand the state of the vibration-reduction lens group VR when correctingimage blur is also illustrated.

Respective reference symbols in FIG. 1 associated with Example 1 areused independently in respective examples in order to avoid complicationof description due to an increased number of reference symbolcharacters. Therefore, even when components in diagrams associated withother examples are denoted by the same reference symbols as used in FIG.1 , these components do not necessarily have the same configuration asthose of other examples.

Tables 1 and 2 illustrated below are tables of respective specificationsof Examples 1 and 2.

In the respective examples, the d-line (wavelength: 587.562 nm) and theg-line (wavelength: 435.835 nm) are selected as an aberrationcharacteristics calculation target.

In [Lens Specification] in tables, a surface number indicates a sequencenumber of an optical surface from an object side along a travelingdirection of light, R indicates a radius of curvature of each opticalsurface, D indicates a surface distance which is the distance on theoptical axis from each optical surface to the next optical surface (oran image plane), nd indicates a refractive index for the d-line, of amaterial of an optical member, and vd indicates the Abbe number for thed-line, of a material of an optical member. Moreover, Di indicates asurface distance between an i-th surface and an (i+1)th surface andAperture stop indicates an aperture stop S. When the optical surface isan aspherical surface, a mark “*” is assigned to the surface number anda paraxial radius of curvature is shown in the radius of curvaturecolumn R.

In [Aspheric Data] in tables, the shape of an aspherical surface shownin [Lens Specification] is expressed by Equation (a) below. X(y)indicates the distance along the optical axis direction from atangential plane at the vertex of an aspherical surface to a position onthe aspherical surface at a height y, R indicates a radius of curvature(a paraxial radius of curvature) of a reference spherical surface, κindicates a conic constant, and Ai indicates an aspheric coefficient atdegree i. “E-n” indicates “×10⁻¹¹”. For example, 1.234E-05=1.234×10⁻⁵.An aspheric coefficient A2 at degree 2 is 0 and is not illustrated.X(y)=(y ² /R)/{1+(1−κ×y ² /R ²)^(1/2) }±A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y¹⁰  (a)

In [Various Data] in tables, f indicates a focal length of an entirelens system, FNo indicates the F-number, ω indicates a half-angle ofview (unit: °), Y indicates the maximum image height, BF indicates thedistance (an air-conversion length) from the last lens surface to theimage plane I on the optical axis upon focusing on an object atinfinity, and TL indicates the sum of BF and the distance from thefrontmost lens surface to the last lens surface on the optical axis uponfocusing on an object at infinity.

In [Variable Distance Data] in tables, Di indicates a surface distancebetween an i-th surface and an (i+1)th surface, D0 indicates an axialair distance between an object plane and a lens surface closest to anobject, of the first lens group G1, f indicates the focal length of anentire lens system, and β indicates an imaging magnification.

In [Lens Group Data] in tables, the starting surface and the focallength of the lens groups are shown.

In [Conditional Expression Correspondence Values] in tables, valuescorresponding to Conditional Expressions (5) to (8) are illustrated.

Hereinafter, “mm” is generally used as the unit of the focal length f,the radius of curvature R, the surface distance D, and other lengths andthe like described in all specification values unless particularlystated otherwise. However, the unit is not limited to this since anequivalent optical performance is obtained even when the optical systemis proportionally expanded or reduced. Moreover, the unit is not limitedto “mm” and other appropriate units may be used.

The above description of tables is common to all examples, anddescription thereof will not be provided below.

Example 1

Example 1 will be described with reference to FIGS. 1 to 4 and Table 1.As illustrated in FIG. 1 , a variable magnification optical system ZL(ZL1) according to Example 1 is constituted by, in order from an object,a first lens group G1 having a negative refractive power; a second lensgroup G2 having a positive refractive power; a third lens group G3having a positive refractive power; a fourth lens group G4 having anegative refractive power; and a fifth lens group G5 having a positiverefractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, abiconvex lens L21 and a cemented lens including a negative meniscus lensL22 having a concave surface oriented toward the image side and apositive meniscus lens L23 having a convex surface oriented toward theobject side.

The third lens group G3 is constituted by a cemented lens including, inorder from the object, a biconvex lens L31 and a negative meniscus lensL32 having a concave surface oriented toward the object side.

The fourth lens group G4 is constituted by, in order from the object, a41st lens group G41 having a negative refractive power and a 42nd lensgroup G42 having a negative refractive power. The 41st lens group G41 isconstituted by, in order from the object, a biconcave lens L41 and abiconvex lens L42. The 42nd lens group G42 is constituted by a cementedlens including, in order from the object, a biconcave lens L43 and apositive meniscus lens L44 having a convex surface oriented toward theobject side. The positive meniscus lens L44 has an aspherical image-sidesurface.

The fifth lens group G5 is constituted by, in order from the object, abiconvex lens L51, a cemented lens including a biconvex lens L52 and abiconcave lens L53, and a cemented lens including a biconvex lens L54and a biconcave lens L55. The biconcave lens L55 has an asphericalimage-side surface.

An aperture stop S is provided between the third lens group G3 and thefourth lens group G4, and the aperture stop S forms the fourth lensgroup G4.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by fixing the first lens group G1 in relation to theimage plane, moving the second lens group G2 toward the object side,moving the third lens group G3 toward the object side, moving the fourthlens group G4 toward the object side, and moving the fifth lens group G5toward the object side such that the distances between the respectivelens groups (the distance between the first and second lens groups G1and G2, the distance between the second and third lens groups G2 and G3,the distance between the third and fourth lens groups G3 and G4, and thedistance between the fourth and fifth lens groups G4 and G5) arechanged. The aperture stop S is moved toward the object side integrallywith the fourth lens group G4.

Focusing from an object at infinity to an object at a close distance isperformed by moving the second lens group G2 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the 42nd lens group G42 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K. The 41st lens group G41 positioned at an object-side ofthe 42nd lens group G42 is immovable during image blur correction.

In Example 1, in the wide-angle end state, since the vibration reductioncoefficient is −0.74 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.31 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −0.90 and the focallength is 23.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.68° is −0.31 mm. In thetelephoto end state, since the vibration reduction coefficient is −1.16and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.29 mm.

Table 1 illustrates the values of respective specifications ofExample 1. Surface numbers 1 to 32 in Table 1 correspond to opticalsurfaces of m1 to m32 illustrated in FIG. 1 .

TABLE 1 [Lens Specification] Surface number R D nd νd *1 144.72719 3.0001.76690 46.9 *2 16.78385 12.144  1.00000 *3 −146.50988 1.700 1.7669046.9 4 112.07990 2.219 1.00000 5 −201.75172 1.700 1.49700 81.7 650.54104 1.200 1.00000 7 47.54818 5.221 1.75520 27.6 8 −219.28043 (D8) 1.00000 9 46.75733 3.989 1.64769 33.7 10 −272.45513 0.100 1.00000 1150.36118 1.000 1.84666 23.8 12 19.87141 4.835 1.60342 38.0 13 62.52826(D13) 1.00000 14 48.51662 6.297 1.49700 81.7 15 −35.93964 1.400 1.8466623.8 16 −54.11218 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18−42.29429 1.300 1.90366 31.3 19 142.58723 0.100 1.00000 20 81.263533.890 1.84666 23.8 21 −56.98684 2.000 1.00000 22 −67.55578 1.300 1.8040046.6 23 33.77804 3.516 1.80518 25.4 *24 150.14014 (D24) 1.00000 2532.07862 7.401 1.49700 81.7 26 −48.27408 0.100 1.00000 27 44.80816 8.0541.49700 81.7 28 −28.00000 1.500 1.74950 35.2 29 112.01929 0.500 1.0000030 60.44099 6.300 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0 *32983.65534 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 2.21315e−06 −2.13704e−09  −5.22294e−12   7.89630e−15 20.00000e+00 9.86610e−06 −4.32155e−09  1.14702e−10 −3.66795e−13 31.00000e+00 −2.67699e−06  1.28816e−10 4.17268e−11 −1.97814e−13 241.00000e+00 −1.85215e−06  1.82819e−10 7.49821e−12 −1.11725e−14 321.00000e+00 1.67690e−05 8.61235e−09 1.61417e−11  9.86306e−15 [VariableData] W M T f 16.40 23.50 34.00 FNo 2.85 2.84 2.85 ω 53.9 40.6 30.1 Y20.00 20.00 20.00 TL 159.619 159.618 159.618 BF 27.426 36.177 49.659[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 340.38 340.38 340.38 β — — — −0.0451 −0.0649 −0.0941f 16.40 23.50 34.00 — — — D8 25.600 10.000 2.000 27.097 11.678 3.852 D135.565 12.410 5.867 4.069 10.733 4.016 D16 3.000 9.997 14.864 3.000 9.99714.864 D24 12.000 5.006 1.200 12.000 5.006 1.200 D32 27.426 36.17749.659 27.426 36.177 49.659 [Lens Group Data] Lens group Startingsurface Focal length 1st lens group 1 −22.99 2nd lens group 9 81.72 3rdlens group 14 62.91 4th lens group 17 −50.13 41st lens group 17 −648.1142nd lens group 22 −57.48 5th lens group 25 38.14 [ConditionalExpression Correspondence Values] Conditional Expression (1) f42/f4 =1.15 Conditional Expression (2) f4/f41 = 0.077 Conditional Expression(3) f1/f4 = 0.459 Conditional Expression (4) A(T3.5)/A(T4.0) = 1.735(A(T3.5) = −0.0180, A(T4.0) = −0.0104)

It can be understood from Table 1 that the variable magnificationoptical system ZL1 according to Example 1 satisfies ConditionalExpressions (1) to (4).

FIG. 2 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration(lateral chromatic aberration), and lateral aberration) upon focusing onan object at infinity, of the variable magnification optical system ZL1according to Example 1, in which part (a) illustrates the wide-angle endstate, part (b) illustrates the intermediate focal length state, andpart (c) illustrates the telephoto end state. FIG. 3 shows graphsillustrating various aberrations (spherical aberration, astigmatism,distortion, magnification chromatic aberration, and lateral aberration)upon focusing on an object at a close point, of the variablemagnification optical system ZL1 according to Example 1, in which part(a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state. FIG. 4 shows graphs illustrating lateral aberration of thevariable magnification optical system ZL1 according to Example 1 whenimage blur correction is performed upon focusing on an object atinfinity, in which part (a) illustrates the wide-angle end state, part(b) illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state.

In the graphs illustrating respective aberrations, FNO indicates theF-number, NA indicates a numerical aperture, A indicates a half-angle ofview (unit: °) at each image height, and HO indicates an object height.d indicates aberration at the d-line and g indicates aberration at theg-line. Moreover, aberrations without these characters indicateaberrations at the d-line. In the graphs illustrating the sphericalaberration upon focusing on an object at infinity, the F-number valuescorresponding to the maximum aperture are illustrated. In the graphsillustrating the spherical aberration upon focusing on an object at aclose point, the numerical aperture values corresponding to the maximumaperture are illustrated. In the graphs illustrating the astigmatism, asolid line indicates the sagittal image plane and a broken lineindicates the meridional image plane.

The same reference symbols as in this example are used in the aberrationgraphs of respective examples to be described later.

It can be understood from FIGS. 2 to 4 that the variable magnificationoptical system ZL1 according to Example 1 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL1 has an excellent imagingperformance upon image blur correction.

Example 2

Example 2 will be described with reference to FIGS. 5 to 8 and Table 2.As illustrated in FIG. 5 , a variable magnification optical system ZL(ZL2) according to Example 2 is constituted by, in order from an object,a first lens group G1 having a negative refractive power; a second lensgroup G2 having a positive refractive power; a third lens group G3having a positive refractive power; a fourth lens group G4 having anegative refractive power; and a fifth lens group G5 having a positiverefractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, abiconvex lens L21 and a cemented lens including a negative meniscus lensL22 having a concave surface oriented toward the image side and apositive meniscus lens L23 having a convex surface oriented toward theobject side.

The third lens group G3 is constituted by a biconvex lens L31.

The fourth lens group G4 is constituted by, in order from the object, a41st lens group G41 having a negative refractive power and a 42nd lensgroup G42 having a negative refractive power. The 41st lens group G41 isconstituted by, in order from the object, a biconcave lens L41 and abiconvex lens L42. The 42nd lens group G42 is constituted by a cementedlens including, in order from the object, a biconcave lens L43 and apositive meniscus lens L44 having a convex surface oriented toward theobject side. The positive meniscus lens L44 has an aspherical image-sidesurface.

The fifth lens group G5 is constituted by, in order from the object, acemented lens including a biconvex lens L51 and a negative meniscus lensL52 having a concave surface oriented toward the object side, a cementedlens including a negative meniscus lens L53 having a concave surfaceoriented toward the image side and a biconvex lens L54, and a negativemeniscus lens L55 having a concave surface oriented toward the objectside. The negative meniscus lens L55 has an aspherical image-sidesurface.

An aperture stop S is provided between the third lens group G3 and thefourth lens group G4, and the aperture stop S forms the fourth lensgroup G4.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by moving the first lens group G1 toward the imageside and then moving the same toward the object side, moving the secondlens group G2 toward the object side, moving the third lens group G3toward the object side, moving the fourth lens group G4 toward theobject side, and moving the fifth lens group G5 toward the object sidesuch that the distances between the respective lens groups (the distancebetween the first and second lens groups G1 and G2, the distance betweenthe second and third lens groups G2 and G3, the distance between thethird and fourth lens groups G3 and G4, and the distance between thefourth and fifth lens groups G4 and G5) are changed. The aperture stop Sis moved toward the object side integrally with the fourth lens groupG4.

Focusing from an object at infinity to an object at a close distance isperformed by moving the second lens group G2 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the 42nd lens group G42 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K. The 41st lens group G41 positioned at an object-side ofthe 42nd lens group G42 is immovable during image blur correction.

In Example 2, in the wide-angle end state, since the vibration reductioncoefficient is −0.65 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.36 mm.

In the intermediate focal length state, since the vibration reductioncoefficient is −0.76 and the focal length is 23.50 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.68° is −0.37 mm. In the telephoto end state, sincethe vibration reduction coefficient is −0.99 and the focal length is34.00 mm, the moving distance of the vibration-reduction lens group VRfor correcting the rotation blur of 0.57° is −0.34 mm.

Table 2 illustrates the values of respective specifications of Example2. Surface numbers 1 to 31 in Table 2 correspond to optical surfaces ofm1 to m31 illustrated in FIG. 5 .

TABLE 2 [Lens Specification] Surface number R D nd νd *1 155.70823 3.0001.76690 46.9 *2 16.71640 13.373  1.00000 *3 −200.00000 1.800 1.7669046.9 4 150.01535 2.786 1.00000 5 −91.03331 1.700 1.49782 82.6 6143.99051 1.200 1.00000 7 58.46345 4.345 1.75520 27.6 8 −434.09219 (D8) 1.00000 9 63.66223 3.791 1.57957 53.7 10 −122.54394 0.100 1.00000 1162.33486 1.400 1.84666 23.8 12 22.85521 4.835 1.60342 38.0 13 130.87641(D13) 1.00000 14 64.13663 4.239 1.49782 82.6 15 −84.26911 (D15) 1.0000016 (Aperture stop) 3.263 1.00000 17 −45.56608 1.000 1.80400 46.6 183172.25670 0.100 1.00000 19 102.14214 2.827 1.84666 23.8 20 −141.923932.000 1.00000 21 −108.76161 1.000 1.80400 46.6 22 29.84706 3.696 1.8051825.4 *23 110.49500 (D23) 1.00000 24 33.41270 8.825 1.49782 82.6 25−24.42987 1.500 1.80440 39.6 26 −40.93874 0.100 1.00000 27 30.634151.500 1.80100 34.9 28 16.29239 13.887  1.49782 82.6 29 −35.27572 1.9381.00000 30 −31.58375 2.000 1.80604 40.7 *31 −200.00000 (D31) 1.00000[Aspheric Data] Surface κ A4 A6 A8 A10 1 1.00000e+00 1.06028e−06 1.59159e−09 −7.12097e−12   6.57046e−15 2 0.00000e+00 6.61060e−06−1.49507e−09 8.61304e−11 −2.65762e−13 3 1.00000e+00 −3.92122e−06 −4.32274e−09 3.03947e−11 −1.42986e−13 23 1.00000e+00 −1.67719e−06 −3.27153e−09 3.18352e−11 −8.33990e−14 31 1.00000e+00 8.89940e−06−7.38491e−09 2.38442e−11 −1.86910e−13 [Various Data] W M T f 16.40 23.5034.00 FNo 2.90 2.89 2.89 ω 53.8 40.4 30.1 Y 20.00 20.00 20.00 TL 161.618157.904 159.837 BF 27.338 34.304 48.377 [Variable Distance Data]Focusing on infinity Focusing on close point W M T W M T D0 ∞ ∞ ∞ 338.38342.10 340.16 β — — — −0.0452 −0.0644 −0.0939 f 16.40 23.50 34.00 — — —D8 25.186 11.390 2.000 26.735 13.032 3.804 D13 7.484 7.667 5.628 5.9356.025 3.825 D15 3.000 11.823 16.426 3.000 11.823 16.426 D23 12.405 6.5151.200 12.405 6.515 1.200 D31 27.338 34.304 48.377 27.338 34.304 48.377[Lens Group Data] Lens group Starting surface Focal distance 1st lensgroup 1 −23.61 2nd lens group 9 79.09 3rd lens group 14 73.86 4th lensgroup 16 −53.41 41st lens group 16 −294.62 42nd lens group 21 −67.66 5thlens group 24 38.67 [Conditional Expression Correspondence Values]Conditional Expression (1) f42/f4 = 1.27 Conditional Expression (2)f4/f41 = 0.181 Conditional Expression (3) f1/f4 = 0.442 ConditionalExpression (4) A(T3.5)/A(T4.0) = 1.759 (A(T3.5) = −0.0183, A(T4.0) =−0.0104)

It can be understood from Table 2 that the variable magnificationoptical system ZL2 according to Example 2 satisfies ConditionalExpressions (1) to (4).

FIG. 6 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL2 according to Example 2, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 7 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL2 according to Example 2, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 8shows graphs illustrating lateral aberration of the variablemagnification optical system ZL2 according to Example 2 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

It can be understood from FIGS. 6 to 8 that the variable magnificationoptical system ZL2 according to Example 2 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL2 has an excellent imagingperformance upon image blur correction.

According to the above-described examples, it is possible to implement avariable magnification optical system which has a bright F-value ofapproximately F2.8 and such a wide angle of view that the half-angle ofview is approximately 50° or more, and in which various aberrations arecorrected satisfactorily.

While the present invention has been described by assigning referencesymbols to elements of the embodiment for better understanding of thepresent invention, the aspect of the present invention is not limited tothis. The following content can be appropriately employed within a rangewhere the optical performance of the variable magnification opticalsystem is not diminished.

Although the numbered examples of a five-group configuration have beenillustrated as numbered examples of the variable magnification opticalsystem ZL, the present invention is not limited to this and can beapplied to other group configurations (for example, a six-groupconfiguration or the like). Specifically, a configuration in which alens or a lens group is added to the side closest to the object side anda configuration in which a lens or a lens group is added to the sideclosest to the image side may be employed. The first lens group G1 maybe divided into a plurality of lens groups, and the respective lensgroups may be moved along different trajectories upon varyingmagnification or one of them may be fixed. In the examples, although the41st lens group G41 has a negative refractive power, the 41st lens groupG41 may have a positive refractive power. Moreover, in the examples,although the 42nd lens group G42 has a negative refractive power, the42nd lens group G42 may have a positive refractive power. A lens grouprefers to a portion having at least one lens isolated by air space whichchanges upon varying magnification or focusing.

In the variable magnification optical system ZL, a portion of a lensgroup, an entire lens group, or a plurality of lens groups may be movedin the optical axis direction as a focusing lens group in order toperform focusing from an object at infinity to an object at a closedistance. Moreover, such a focusing lens group can be applied toautofocus and is also suitable for driving based on an autofocus motor(for example, an ultrasonic motor, a step motor, a voice coil motor, orthe like). As described above, although it is most preferable that theentire second lens group G2 is configured as a focusing lens group, aportion of the second lens group G2 may be configured as a focusing lensgroup. Moreover, although the focusing lens group may include one singlelens and one cemented lens described above, the number of lenses is notparticularly limited and the focusing lens group may include one or morelens components.

In the variable magnification optical system ZL, an entire arbitrarylens group or a partial lens group may be moved so as to have acomponent in the direction orthogonal to the optical axis or may berotated (oscillated) in an in-plane direction including the optical axisso as to function as a vibration-reduction lens group that correctsimage blur occurring due to camera shake or the like. As describedabove, it is most preferable that a portion of the fourth lens group G4is configured as the vibration-reduction lens group. Moreover, althoughthe vibration-reduction lens group may be constituted by one cementedlens as described above, the number of lenses is not particularlylimited and the vibration-reduction lens group may be constituted by onesingle lens or a plurality of lens components. Moreover, thevibration-reduction lens group may have a positive refractive power andit is preferable that the entire fourth lens group G4 have a negativerefractive power.

In the variable magnification optical system ZL, the lens surface may beformed as a spherical surface or a flat surface and may be formed as anaspherical surface. When the lens surface is a spherical surface or aflat surface, it is possible to facilitate lens processing, assembly,and adjustment and to prevent deterioration of optical performanceresulting from errors in the processing, assembly and adjustment.Moreover, deterioration of the rendering performance is little even whenthe image plane is shifted. When the lens surface is an asphericalsurface, the aspherical surface may be an aspherical surface obtained bygrinding a glass-molded aspherical surface obtained by molding glassinto an aspherical surface, or a composite aspherical surface obtainedby forming a resin on the surface of glass into an aspherical shape.Moreover, the lens surface may be a diffraction surface and may be arefractive index distributed lens (a GRIN lens) or a plastic lens.

In the variable magnification optical system ZL, it is preferable thatthe aperture stop S be disposed in the fourth lens group G4 so as to beintegrated with the 41st lens group G41. However, the aperture stop Smay be configured so as to be movable separately from the 41st lensgroup G41. Moreover, the role of the aperture stop may be substituted bythe frame of a lens without providing a separate member as the aperturestop.

In the variable magnification optical system ZL, each lens surface maybe coated with an anti-reflection film which has high transmittance in awide wavelength region in order to decrease flare and ghosting andachieve satisfactory optical performance with high contrast. The type ofthe anti-reflection film may be selected appropriately. Moreover, thenumber of anti-reflection films and the position thereof may be selectedappropriately. In Examples 1 and 2, it is preferable that any one of theimage-side surface of the lens L11, the object-side surface of the lensL12, the image-side surface of the lens L12, the image-side surface ofthe lens L13, and the object-side surface of the lens L14 of the firstlens group G1 or a plurality of surfaces be coated with ananti-reflection film which has high transmittance in a wavelengthregion.

The variable magnification ratio (variable power ratio) of the variablemagnification optical system ZL may be between approximately 1.5 and2.5, for example. Moreover, the focal length (a value converted in termsof a 35-mm thick plate) in the wide-angle end state of the variablemagnification optical system ZL may be between approximately 15 and 20mm, for example. Moreover, the F-value in the wide-angle end state ofthe variable magnification optical system ZL may be betweenapproximately 2.7 and 3.5, for example. Moreover, the F-value in thetelephoto end state of the variable magnification optical system ZL maybe between approximately 2.7 and 3.5, for example. Furthermore, when thefocusing state of the variable magnification optical system ZL changesfrom the wide-angle end state to the telephoto end state, the F-valuemay be approximately constant (a variation is equal to or smaller than10 percent of the F-value in the telephoto end state).

Another embodiment will now be described with reference to the drawings.FIG. 9 illustrates an example of a configuration of a variablemagnification optical system ZL. In other examples, the number of lensgroups, a lens configuration of each lens group, and the like can bechanged appropriately.

In an embodiment, a variable magnification optical system includes, inorder from an object, a first lens group G1 having a negative refractivepower, a second lens group G2 having a positive refractive power, athird lens group G3, a fourth lens group G4, and a fifth lens group G5having a positive refractive power, the system performing varyingmagnification by changing the distance between the first and second lensgroups G1 and G2, the distance between the second and third lens groupsG2 and G3, the distance between the third and fourth lens groups G3 andG4, and the distance between the fourth and fifth lens groups G4 and G5,and at least a portion of the fourth lens group G4 is configured to bemovable so as to have a component in the direction orthogonal to anoptical axis. In an example, the fourth lens group G4 has a negativerefractive power.

Alternatively, a variable magnification optical system ZL may include,in order from an object, a first lens group G1 having a negativerefractive power, a second lens group G2 having a positive refractivepower, a third lens group G3, a fourth lens group G4 having a negativerefractive power, and a fifth lens group G5 having a positive refractivepower, the system performing varying magnification by changing thedistances between the respective lens groups, and at least a portion ofthe fourth lens group G4 may be configured to be movable so as to have acomponent in the direction orthogonal to an optical axis in order tocorrect image blur as a vibration-reduction lens group VR.

The variable magnification optical system has the first lens group G1having a negative refractive power, the second lens group G2 having apositive refractive power, the third lens group G3, the fourth lensgroup G4 having a negative refractive power, and the fifth lens group G5having a positive refractive power and changes the distances between therespective lens groups. Therefore, it is possible to implement avariable magnification optical system having a wide angle of view.Moreover, at least a portion of the fourth lens group G4 having anegative refractive power is moved so as to have a component in thedirection orthogonal to the optical axis to perform image blurcorrection. Therefore, it is possible to suppress the occurrence ofeccentric coma aberration (decentering coma aberration) and one-sidedblur during image blur correction and to obtain satisfactory imagingperformance.

The third lens group G3 may have a positive refractive power or anegative refractive power.

The fourth lens group G4 may include one or more lenses which areimmovable during image blur correction in addition to thevibration-reduction lens group VR.

The variable magnification optical system ZL satisfies ConditionalExpressions (5) and (6) below.−0.400<(D34T−D34W)/(D23T−D23W)<1.000  (5)−0.400<f4/f3<0.450  (6)

where

D34T: an air distance between the third and fourth lens groups G3 and G4in a telephoto end state

D34W: an air distance between the third and fourth lens groups G3 and G4in a wide-angle end state

D23T: an air distance between the second and third lens groups G2 and G3in a telephoto end state

D23W: an air distance between the second and third lens groups G2 and G3in a wide-angle end state

f4: a focal length of the fourth lens group G4

f3: a focal length of the third lens group G3

Conditional Expression (5) is a conditional expression for defining anappropriate ratio between a change in the distance between the third andfourth lens groups G3 and G4 and a change in the distance between thesecond and third lens groups G2 and G3 upon varying magnification fromthe wide-angle end state to the telephoto end state. When ConditionalExpression (5) is satisfied, it is possible to obtain a bright F-value(approximately F2.8 to F3.5) and to satisfactorily correct variousaberrations including spherical aberration while maintaining a varyingmagnification effect.

If the ratio exceeds the upper limit value of Conditional Expression(5), the ratio of a change in the distance between the third and fourthlens groups G3 and G4 to a change in the distance between the second andthird lens groups G2 and G3 increases toward the positive side whereasthe change in the distance between the second and third lens groups G2and G3 decreases relatively, and the varying magnification effectdecreases. As a result, it is difficult to secure a variablemagnification ratio and a wide angle of view.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (5) be set to 0.800. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (5) be set to 0.600.

If the ratio is smaller than the lower limit value of ConditionalExpression (5), the ratio of a change in the distance between the thirdand fourth lens groups G3 and G4 to a change in the distance between thesecond and third lens groups G2 and G3 increases toward the negativeside whereas the change in the distance between the second and thirdlens groups G2 and G3 decreases relatively, and the varyingmagnification effect decreases. As a result, it is difficult to secure avariable magnification ratio and a wide angle of view.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (5) be set to −0.300. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (5) be set to −0.200.

Conditional Expression (6) is a conditional expression for defining anappropriate focal length ratio between the fourth and third lens groupsG4 and G3. When Conditional Expression (6) is satisfied, it is possibleto control a moving distance of the fourth lens group G4 moved duringimage blur correction appropriately while obtaining satisfactory imagingperformance during image blur correction.

If the focal length ratio exceeds the upper limit value of ConditionalExpression (6), the negative refractive power of the third lens group G3increases, the negative refractive power of the fourth lens group G4decreases, and the moving distance of the fourth lens group G4 movedduring image blur correction increases. As a result, the size of animage blur correction mechanism is increased and the size of the entirelens is increased.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (6) be set to 0.400. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (6) be set to 0.350.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (6), the positive refractive power of the thirdlens group G3 increases, the negative refractive power of the fourthlens group G4 increases, and the occurrence of eccentric aberration whenthe fourth lens group G4 is moved so as to have a component in thedirection orthogonal to the optical axis during image blur correctionincreases. As a result, the occurrence of one-sided blur or eccentriccoma aberration occurring during image blur correction increases, and itis difficult to maintain satisfactory imaging performance.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (6) be set to −0.350. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (6) be set to −0.300.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (7) below.0.200<f1/f4<0.900  (7)

where

f1: a focal length of the first lens group G1

Conditional Expression (7) is a conditional expression forsatisfactorily correcting curvature of field and coma aberration whileobtaining a wide angle of view (a half-angle of view of approximately50° or more) in the wide-angle end state.

If the focal length ratio exceeds the upper limit value of ConditionalExpression (7), the focal length of the first lens group G1 is increasedand it is difficult to obtain a wide angle of view (a half-angle of viewof approximately 50° or more) in the wide-angle end state. In somecases, a total length and a lens diameter of the first lens group G1 areincreased undesirably.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (7) be set to 0.800. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (7) be set to 0.700.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (7), the focal length of the first lens group G1is decreased and it is difficult to correct curvature of field and comaaberration and to obtain satisfactory imaging performance.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (7) be set to 0.250. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (7) be set to 0.300.

In the variable magnification optical system ZL, it is preferable thatthe third lens group G3 have a negative lens and a positive lens.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the fourth lens groupG4 is moved to perform image blur correction. Moreover, it is possibleto effectively correct various aberrations including sphericalaberration and astigmatism upon varying magnification.

In the variable magnification optical system ZL, it is preferable thatthe fourth lens group G4 be constituted by a cemented lens including apositive lens and a negative lens.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the fourth lens groupG4 is moved to perform image blur correction. Moreover, it is possibleto decrease the size and the weight of a lens that moves for image blurcorrection and to effectively decrease the size of an image blurcorrection mechanism and the entire lens.

The fourth lens group G4 may include two lenses (separated from abonding surface) instead of bonding a positive lens and a negative lensas described above.

In the variable magnification optical system ZL, it is preferable thatthe lens surface closest to an image, of the fourth lens group G4 be anaspherical surface.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the fourth lens groupG4 is moved to perform image blur correction.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (8) below.1.100<A(T3.5)/A(T4.0)<5.000  (8)

where

A(T3.5): an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 3.5 passes through the aspherical surface ina telephoto end state

A(T4.0): an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 4.0 passes through the aspherical surface ina telephoto end state

The asphericity refers to an amount of sag, with respect to anapproximately spherical surface, in the aspherical surface along theoptical axis.

Conditional Expression (8) is a Conditional Expression for defining anappropriate value of the asphericity of the aspherical surface closestto an image, of the fourth lens group G4. When Conditional Expression(8) is satisfied, it is possible to satisfactorily correct one-sidedblur and eccentric coma aberration when the fourth lens group G4 ismoved to perform image blur correction.

When the asphericity ratio exceeds the upper limit value of ConditionalExpression (8), the asphericity of the fourth lens group G4 becomes toolarge and it is difficult to correct one-sided blur and eccentric comaaberration when the fourth lens group G4 is moved to perform image blurcorrection.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (8) be set to 4.000. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (8) be set to 3.000.

When the asphericity ratio is smaller than the lower limit value ofConditional Expression (8), the asphericity of the fourth lens group G4is insufficient and it is difficult to correct one-sided blur andeccentric coma aberration when the fourth lens group G4 is moved toperform image blur correction.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (8) be set to 1.250. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (8) be set to 1.400.

In the variable magnification optical system ZL, it is preferable thatthe third lens group G3 be immovable in relation to the image plane uponvarying magnification similarly to Example 4 to be described later, forexample.

According to this configuration, it is possible to simplify a varyingmagnification mechanism and to effectively decrease the size and thecost and to secure an imaging performance due to a reduced eccentricerror. Moreover, this effect is significant when a diaphragm isintegrated with the third lens group G3.

In the variable magnification optical system ZL, it is preferable thatthe fourth lens group G4 be immovable in relation to the image planeupon varying magnification similarly to Example 5 to be described later,for example.

According to this configuration, it is possible to simplify a varyingmagnification mechanism and to effectively decrease the size and thecost. Moreover, since the fourth lens group G4 is a vibration-reductionlens group VR, it is not necessary to move an image blur correctionmechanism in the optical axis direction and it is possible toparticularly effectively reduce the entire lens size.

In the variable magnification optical system ZL, it is preferable thatfocusing be performed by moving the second lens group G2 in the opticalaxis direction as a focusing lens group.

According to this configuration, it is possible to decrease the size andthe weight of a focusing lens group and to decrease the size of anentire lens system and to increase a focusing speed during autofocus.

In this way, it is possible to implement the variable magnificationoptical system ZL which has a bright F-value and a wide angle of viewand in which various aberrations are corrected satisfactorily.

The above-described variable magnification optical system ZL may beincluded in the camera (an optical apparatus) illustrated in FIG. 33 .

As can be understood from respective examples to be described later, thevariable magnification optical system ZL mounted on the camera 1 as theimage capturing lens 2 has a bright F-value and a wide angle of view andhas a satisfactory optical performance such that various aberrations arecorrected satisfactorily due to its characteristic lens configuration.Therefore, according to the camera 1, it is possible to implement anoptical apparatus which has a bright F-value and a wide angle of viewand has a satisfactory optical performance such that various aberrationsare corrected satisfactorily.

Although a mirrorless camera has been described as an example of thecamera 1, the camera is not limited to this. For example, the sameeffect as the camera 1 can be obtained even when the above-describedvariable magnification optical system ZL is mounted on a single-lensreflex camera which has a quick return mirror on a camera body and viewsa subject using a finder optical system.

Next, an example of a method for manufacturing the above-describedvariable magnification optical system ZL will be described. FIGS. 36 and37 illustrate an example of a method for manufacturing the variablemagnification optical system ZL.

In the example illustrated in FIG. 36 , first, respective lensesincluding a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3; a fourth lens group G4; and a fifth lens group G5 having apositive refractive power are arranged, in order from an object, in alens barrel such that varying magnification is performed by changing thedistance between the first and second lens groups G1 and G2, thedistance between the second and third lens groups G2 and G3, thedistance between the third and fourth lens groups G3 and G4, and thedistance between the fourth and fifth lens groups G4 and G5 (step ST1).The respective lenses are arranged such that at least a portion of thefourth lens group G4 is configured to be movable so as to have acomponent in the direction orthogonal to the optical axis (step ST2).The respective lenses are arranged so as to satisfy ConditionalExpressions (5) and (6) below (step ST3).−0.400<(D34T−D34W)/(D23T−D23W)<1.000  (5)−0.400<f4/f3<0.450  (6)

where

D34T: an air distance between the third and fourth lens groups G3 and G4in a telephoto end state

D34W: an air distance between the third and fourth lens groups G3 and G4in a wide-angle end state

D23T: an air distance between the second and third lens groups G2 and G3in a telephoto end state

D23W: an air distance between the second and third lens groups G2 and G3in a wide-angle end state

f4: a focal length of the fourth lens group G4

f3: a focal length of the third lens group G3

In the example illustrated in FIG. 37 , first, respective lensesincluding a first lens group G1 having a negative refractive power, asecond lens group G2 having a positive refractive power, a third lensgroup G3, a fourth lens group G4 having a negative refractive power, anda fifth lens group G5 having a positive refractive power are arranged,in order from an object, in a lens barrel such that varyingmagnification is performed by changing the distances between therespective lens groups (step ST10).

The respective lenses are arranged such that at least a portion of thefourth lens group G4 is configured to be movable so as to have acomponent in the direction orthogonal to the optical axis in order tocorrect image blur (step ST20). The respective lenses are arranged so asto satisfy Conditional Expressions (5) and (6) below (step ST30).−0.400<(D34T−D34W)/(D23T−D23W)<1.000  (5)−0.400<f4/f3<0.450  (6)

where

D34T: an air distance between the third and fourth lens groups G3 and G4in a telephoto end state

D34W: an air distance between the third and fourth lens groups G3 and G4in a wide-angle end state

D23T: an air distance between the second and third lens groups G2 and G3in a telephoto end state

D23W: an air distance between the second and third lens groups G2 and G3in a wide-angle end state

f4: a focal length of the fourth lens group G4

f3: a focal length of the third lens group G3

According to an example of a lens arrangement, as illustrated in FIG. 9, a negative meniscus lens L11 having a concave surface oriented towardan image side, a biconcave lens L12, a biconcave lens L13, and abiconvex lens L14 are arranged, in order from the object, to form thefirst lens group G1. A biconvex lens L21, a cemented lens including anegative meniscus lens L22 having a concave surface oriented toward theimage side and a positive meniscus lens L23 having a convex surfaceoriented toward the object side and a cemented lens including a biconvexlens L24 and a negative meniscus lens L25 having a concave surfaceoriented toward the object side are arranged, in order from the object,to form the second lens group G2. A biconcave lens L31 and a biconvexlens L32 are arranged, in order from the object, to form the third lensgroup G3. A cemented lens including a biconcave lens L41 and a positivemeniscus lens L42 having a convex surface oriented toward the objectside arranged in order from the object forms the fourth lens group G4. Abiconvex lens L51, a cemented lens including a biconvex lens L52 and abiconcave lens L53, a biconvex lens L54, and a biconcave lens L55 arearranged, in order from the object, to form the fifth lens group G5. Therespective lens groups prepared in this manner are arranged in theabove-described order to manufacture the variable magnification opticalsystem ZL.

According to the above-described manufacturing method, it is possible tomanufacture the variable magnification optical system ZL which has abright F-value and a wide angle of view and in which various aberrationsare corrected satisfactorily.

Hereinafter, respective examples will be described with reference to thedrawings.

FIGS. 9, 13, and 17 are cross-sectional views illustrating theconfiguration and the refractive power allocation of variablemagnification optical systems ZL (ZL1 to ZL3) according to respectiveexamples. In the lower part of the cross-sectional views of the variablemagnification optical systems ZL1 to ZL3, the moving directions alongthe optical axis of each lens group upon varying magnification from thewide-angle end state (W) to the telephoto end state (T) via theintermediate focal length state (M) are indicated by arrows. In theupper part of the cross-sectional views of the variable magnificationoptical systems ZL1 to ZL3, the moving direction of the focusing lensgroup upon focusing from an object at infinity to an object at a closedistance is indicated by an arrow and the state of thevibration-reduction lens group VR when correcting image blur is alsoillustrated.

Respective reference symbols in FIG. 9 associated with Example 3 areused independently in respective examples in order to avoid complicationof description due to an increased number of reference symbolcharacters. Therefore, even when components in diagrams associated withother examples are denoted by the same reference symbols as used in FIG.9 , these components do not necessarily have the same configuration asthose of other examples.

Tables 3 to 5 illustrated below are tables of respective specificationsof Examples 3 to 5.

In the respective examples, the d-line (wavelength: 587.562 nm) and theg-line (wavelength: 435.835 nm) are selected as an aberrationcharacteristics calculation target.

In [Lens Specification] in tables, a surface number indicates a sequencenumber of an optical surface from an object side along a travelingdirection of light, R indicates a radius of curvature of each opticalsurface, D indicates a surface distance which is the distance on theoptical axis from each optical surface to the next optical surface (oran image plane), nd indicates a refractive index for the d-line, of amaterial of an optical member, and vd indicates the Abbe number for thed-line, of a material of an optical member. Moreover, Di indicates asurface distance between an i-th surface and an (i+1)th surface andAperture stop indicates an aperture stop S. When the optical surface isan aspherical surface, a mark “*” is assigned to the surface number anda paraxial radius of curvature is shown in the radius of curvaturecolumn R.

In [Aspheric Data] in tables, the shape of an aspherical surface shownin [Lens Specification] is expressed by Equation (a) below. X(y)indicates the distance along the optical axis direction from atangential plane at the vertex of an aspherical surface to a position onthe aspherical surface at a height y, R indicates a radius of curvature(a paraxial radius of curvature) of a reference spherical surface, κindicates a conic constant, and Ai indicates an aspheric coefficient atdegree i. “E-n” indicates “×10⁻¹¹”. For example, 1.234E-05=1.234×10′. Anaspheric coefficient A2 at degree 2 is 0 and is not illustrated.X(y)=(y ² /R)/{1+(1−κ×y ² /R ²)^(1/2) }±A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y¹⁰  (a)

In [Various Data] in tables, f indicates a focal length of an entirelens system,

FNo indicates the F-number, ω indicates a half-angle of view (unit: °),Y indicates the maximum image height, BF indicates the distance (anair-conversion length) from the last lens surface to the image plane Ion the optical axis upon focusing on an object at infinity, and TLindicates the sum of BF and the distance from the frontmost lens surfaceto the last lens surface on the optical axis upon focusing on an objectat infinity.

In [Variable Distance Data] in tables, Di indicates a surface distancebetween an i-th surface and an (i+1)th surface, D0 indicates an axialair distance between an object plane and a lens surface closest to anobject, of the first lens group G1, f indicates the focal length of anentire lens system, and β indicates an imaging magnification.

In [Lens Group Data] in tables, the starting surface and the focallength of the lens groups are shown.

In [Conditional Expression Correspondence Values] in tables, valuescorresponding to Conditional Expressions (5) to (8) are illustrated.

Hereinafter, “mm” is generally used as the unit of the focal length f,the radius of curvature R, the surface distance D, and other lengths andthe like described in all specification values unless particularlystated otherwise. However, the unit is not limited to this since anequivalent optical performance is obtained even when the optical systemis proportionally expanded or reduced. Moreover, the unit is not limitedto “mm” and other appropriate units may be used.

The above description of tables is common to all examples, anddescription thereof will not be provided below.

Example 3

Example 3 will be described with reference to FIGS. 9 to 12 and Table 3.As illustrated in FIG. 9 , a variable magnification optical system ZL(ZL1) according to Example 3 is constituted by, in order from an object,a first lens group G1 having a negative refractive power; a second lensgroup G2 having a positive refractive power; a third lens group G3having a negative refractive power; a fourth lens group G4 having anegative refractive power; and a fifth lens group G5 having a positiverefractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward animage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, a21st lens group G21 having a positive refractive power and a 22nd lensgroup G22 having a positive refractive power. The 21st lens group G21 isconstituted by, in order from the object, a biconvex lens L21 and acemented lens including a negative meniscus lens L22 having a concavesurface oriented toward the image side and a positive meniscus lens L23having a convex surface oriented toward the object side. The 22nd lensgroup G22 is constituted by a cemented lens, in order from the object,including a biconvex lens L24 and a negative meniscus lens L25 having aconcave surface oriented toward the object side.

The third lens group G3 is constituted by, in order from the object, abiconcave lens L31 and a biconvex lens L32.

The fourth lens group G4 is constituted by a cemented lens including, inorder from the object, a biconcave lens L41 and a positive meniscus lensL42 having a convex surface oriented toward the object side. Thepositive meniscus lens L42 has an aspherical image-side surface.

The fifth lens group G5 is constituted by, in order from the object, abiconvex lens L51, a cemented lens including a biconvex lens L52 and abiconcave lens L53, and a cemented lens including a biconvex lens L54and a biconcave lens L55. The biconcave lens L55 has an asphericalimage-side surface.

An aperture stop S is provided between the second lens group G2 and thethird lens group G3, and the aperture stop S forms the third lens groupG3.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by moving the first lens group G1 toward the imageside and then moving the same toward the object side, moving the secondlens group G2 toward the object side, moving the third lens group G3toward the object side, moving the fourth lens group G4 toward theobject side, and moving the fifth lens group G5 toward the object sidesuch that the distances between the respective lens groups (the distancebetween the first and second lens groups G1 and G2, the distance betweenthe second and third lens groups G2 and G3, the distance between thethird and fourth lens groups G3 and G4, and the distance between thefourth and fifth lens groups G4 and G5) are changed. The aperture stop Sis moved toward the object side integrally with the third lens group G3.

Focusing from an object at infinity to an object at a close distance isperformed by moving the 21st lens group G21 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the fourth lens group G4 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K.

In Example 3, in the wide-angle end state, since the vibration reductioncoefficient is −0.64 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.36 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −0.74 and the focallength is 23.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.68° is −0.38 mm. In thetelephoto end state, since the vibration reduction coefficient is −0.95and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.35 mm.

Table 3 illustrates the values of respective specifications of Example3. Surface numbers 1 to 32 in Table 3 correspond to optical surfaces ofm1 to m32 illustrated in FIG. 9 .

TABLE 3 [Lens Specification] Surface number R D nd νd *1 168.38636 3.0001.76690 46.9 *2 16.71640 12.168  1.00000 *3 −132.14592 1.700 1.7669046.9 4 134.95206 1.900 1.00000 5 −243.29246 1.700 1.49700 81.7 651.76998 1.200 1.00000 7 49.16596 5.282 1.75520 27.6 8 −184.55701 (D8) 1.00000 9 42.28900 4.491 1.64769 33.7 10 −283.89703 0.100 1.00000 1149.70559 0.999 1.84666 23.8 12 19.12296 4.835 1.60342 38.0 13 52.76752(D13) 1.00000 14 53.11057 6.255 1.49700 81.7 15 −33.51166 1.400 1.8466623.8 16 −47.05744 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18−39.36811 1.300 1.90366 31.3 19 217.23501 0.099 1.00000 20 80.071383.361 1.84666 23.8 21 −72.96748 (D21) 1.00000 22 −75.94681 1.300 1.8040046.6 23 32.26272 3.644 1.80518 25.4 *24 182.89657 (D24) 1.00000 2531.94239 7.389 1.49700 81.7 26 −48.60077 0.100 1.00000 27 41.92922 8.2091.49700 81.7 28 −28.00000 1.500 1.74950 35.2 29 117.62625 0.518 1.0000030 67.34233 7.882 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0 *32468.65935 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 1.93012e−06 −2.42361 e−09  −3.50001e−12   6.82597e−15 20.00000e+00 9.23814e−06 −3.45504e−09 9.54947e−11 −3.15535e−13 31.00000e+00 −2.60282e−06  −3.46987e−09 5.33701e−11 −2.20299e−13 241.00000e+00 −1.37016e−06  −1.51547e−09 2.18954e−11 −6.25589e−14 321.00000e+00 1.88211e−05  1.24803e−08 1.76466e−11  3.26274e−14 [VariousData] W M T f 16.40 23.50 34.00 FNo 2.88 2.85 2.87 ω 54.0 39.8 29.5 Y20.00 20.00 20.00 TL 159.620 156.503 159.635 BF 25.339 31.627 44.226[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 340.38 343.50 340.37 β — — — −0.0451 −0.0643 −0.0942f 16.40 23.50 34.00 — — — D8 25.600 11.916 2.000 27.194 13.664 3.990 D136.085 6.085 6.085 4.491 4.337 4.095 D16 3.000 9.806 18.528 3.000 9.80618.528 D21 2.000 5.039 2.000 2.000 5.039 2.000 D24 12.000 6.434 1.20012.000 6.434 1.200 D32 25.339 31.627 44.226 25.339 31.627 44.226 [LensGroup Data] Lens group Starting surface Focal distance 1st lens group 1−23.62 2nd lens group 9 40.58 21st lens group 9 84.14 22nd lens group 1460.13 3rd lens group 17 −235.40 4th lens group 22 −66.32 5th lens group25 37.85 [Conditional Expression Correspondence Values] ConditionalExpression (5) (D34T − D34W)/(D23T − D23W) = 0.000 ConditionalExpression (6) f4/f3 = 0.282 Conditional Expression (7) f1/f4 = 0.356Conditional Expression (8) A(T3.5)/A(T4.0) = 1.736 (A(T3.5) = −0.0112,A(T4.0) = −0.0065)

It can be understood from Table 3 that the variable magnificationoptical system ZL1 according to Example 3 satisfies ConditionalExpressions (5) to (8).

FIG. 10 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL1 according to Example 3, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 11 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL1 according to Example 3, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 12shows graphs illustrating lateral aberration of the variablemagnification optical system ZL1 according to Example 3 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

In the graphs illustrating respective aberrations, FNO indicates theF-number, NA indicates a numerical aperture, A indicates a half-angle ofview (unit: °) at each image height, and HO indicates an object height.d indicates aberration at the d-line and g indicates aberration at theg-line. Moreover, aberrations without these characters indicateaberrations at the d-line. In the graphs illustrating the sphericalaberration upon focusing on an object at infinity, the F-number valuescorresponding to the maximum aperture are illustrated. In the graphsillustrating the spherical aberration upon focusing on an object at aclose point, the numerical aperture values corresponding to the maximumaperture are illustrated. In the graphs illustrating the astigmatism, asolid line indicates the sagittal image plane and a broken lineindicates the meridional image plane.

The same reference symbols as in this example are used in the aberrationgraphs of respective examples to be described later.

It can be understood from FIGS. 10 to 12 that the variable magnificationoptical system ZL1 according to Example 3 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL1 has an excellent imagingperformance upon image blur correction.

Example 4

Example 4 will be described with reference to FIGS. 13 to 16 and Table4. As illustrated in FIG. 13 , a variable magnification optical systemZL (ZL2) according to Example 4 is constituted by, in order from anobject, a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a negative refractive power; a fourth lens group G4having a negative refractive power; and a fifth lens group G5 having apositive refractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, a21st lens group G21 having a positive refractive power and a 22nd lensgroup G22 having a positive refractive power. The 21st lens group G21 isconstituted by, in order from the object, a biconvex lens L21 and acemented lens including a negative meniscus lens L22 having a concavesurface oriented toward the image side and a positive meniscus lens L23having a convex surface oriented toward the object side. The 22nd lensgroup G22 is constituted by a cemented lens including, in order from theobject, a biconvex lens L24 and a negative meniscus lens L25 having aconcave surface oriented toward the object side.

The third lens group G3 is constituted by, in order from the object, anegative meniscus lens L31 having a concave surface oriented toward theobject side and a positive meniscus lens L32 having a convex surfaceoriented toward the image side.

The fourth lens group G4 is constituted by a cemented lens including, inorder from the object, a biconcave lens L41 and a positive meniscus lensL42 having a convex surface oriented toward the object side. Thepositive meniscus lens L42 has an aspherical image-side surface.

The fifth lens group G5 is constituted by, in order from the object, abiconvex lens L51, a cemented lens including a biconvex lens L52 and abiconcave lens L53, and a cemented lens including a biconvex lens L54and a biconcave lens L55. The biconcave lens L55 has an asphericalimage-side surface.

An aperture stop S is provided between the second lens group G2 and thethird lens group G3, and the aperture stop S forms the third lens groupG3.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by moving the first lens group G1 toward the imageside and then moving the same toward the object side, moving the secondlens group G2 toward the object side, fixing the third lens group G3 inrelation to the image plane, moving the fourth lens group G4 toward theimage side and then moving the same toward the object side, and movingthe fifth lens group G5 toward the object side such that the distancesbetween the respective lens groups (the distance between the first andsecond lens groups G1 and G2, the distance between the second and thirdlens groups G2 and G3, the distance between the third and fourth lensgroups G3 and G4, and the distance between the fourth and fifth lensgroups G4 and G5) are changed. The aperture stop S is fixed in relationto the image plane integrally with the third lens group G3.

Focusing from an object at infinity to an object at a close distance isperformed by moving the 21st lens group G21 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the fourth lens group G4 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K.

In Example 4, in the wide-angle end state, since the vibration reductioncoefficient is −0.68 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.34 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −0.76 and the focallength is 24.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.67° is −0.38 mm. In thetelephoto end state, since the vibration reduction coefficient is −0.95and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.35 mm.

Table 4 illustrates the values of respective specifications of Example4. Surface numbers 1 to 32 in Table 4 correspond to optical surfaces ofm1 to m32 illustrated in FIG. 13 .

TABLE 4 [Lens Specification] Surface number R D nd νd *1 193.25434 3.0001.76690 46.9 *2 17.13465 12.086  1.00000 *3 −200.00000 1.700 1.7669046.9 4 99.36571 1.934 1.00000 5 −702.67887 1.700 1.49700 81.7 6 45.421281.200 1.00000 7 45.47188 6.037 1.75520 27.6 8 −335.54839 (D8)  1.00000 952.73871 6.048 1.64769 33.7 10 −167.28882 0.100 1.00000 11 55.014371.000 1.84666 23.8 12 20.79608 4.835 1.60342 38.0 13 68.48478 (D13)1.00000 14 48.68485 6.332 1.49700 81.7 15 −36.34788 1.400 1.84666 23.816 −49.89711 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18 −37.127331.300 1.90366 31.3 19 −213.84119 0.100 1.00000 20 −3697.41390 2.9011.84666 23.8 21 −52.57832 (D21) 1.00000 22 −113.43754 1.300 1.80400 46.623 27.30005 3.766 1.80518 25.4 *24 90.97626 (D24) 1.00000 25 32.823707.685 1.49700 81.7 26 −46.49495 0.100 1.00000 27 47.76928 8.611 1.4970081.7 28 −28.00000 1.500 1.74950 35.2 29 179.04198 0.500 1.00000 3080.91519 5.824 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0 *32728.12773 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 2.55253e−06 −2.06216e−09 −3.73822e−12   6.17187e−15 20.00000e+00 8.20822e−06 −1.94550e−09 8.73648e−11 −2.71723e−13 31.00000e+00 −2.79582e−06  −3.37193e−09 4.74900e−11 −1.88234e−13 241.00000e+00 −1.52089e−06   2.03534e−09 7.28188e−12 −3.57628e−14 321.00000e+00 1.34254e−05  8.78505e−09 −2.82571e−12   6.66429e−14 [VariousData] W M T f 16.40 24.50 34.00 FNo 2.85 2.88 2.87 ω 53.9 38.5 29.6 Y20.00 20.00 20.00 TL 163.818 160.810 162.492 BF 26.615 31.660 41.455[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 336.18 339.19 337.51 β — — — −0.0456 −0.0679 −0.0949f 16.40 24.50 34.00 — — — D8 24.176 10.171 2.298 25.710 11.867 4.175 D135.770 5.770 5.770 4.235 4.074 3.893 D16 3.000 14.001 23.546 3.000 14.00123.546 D21 2.035 4.457 2.000 2.035 4.457 2.000 D24 16.000 8.528 1.20016.000 8.528 1.200 D32 26.615 31.660 41.455 26.615 31.660 41.455 [LensGroup Data] Lens group Starting surface Focal distance 1st lens group 1−23.00 2nd lens group 9 39.44 21st lens group 9 83.59 22nd lens group 1458.05 3rd lens group 17 −297.53 4th lens group 22 −62.23 5th lens group25 38.73 [Conditional Expression Correspondence Values] ConditionalExpression (5) (D34T − D34W)/(D23T − D23W) = −0.002 ConditionalExpression (6) f4/f3 = 0.209 Conditional Expression (7) f1/f4 = 0.370Conditional Expression (8) A(T3.5)/A(T4.0) = 1.694 (A(T3.5) = −0.0079,A(T4.0) = −0.0047)

It can be understood from Table 4 that the variable magnificationoptical system ZL2 according to Example 4 satisfies ConditionalExpressions (5) to (8).

FIG. 14 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL2 according to Example 4, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 15 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL2 according to Example 4, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 16shows graphs illustrating lateral aberration of the variablemagnification optical system ZL2 according to Example 4 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

It can be understood from FIGS. 14 to 16 that the variable magnificationoptical system ZL2 according to Example 4 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL2 has an excellent imagingperformance upon image blur correction.

Example 5

Example 5 will be described with reference to FIGS. 17 to 20 and Table5. As illustrated in FIG. 17 , a variable magnification optical systemZL (ZL3) according to Example 5 is constituted by, in order from anobject, a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a positive refractive power; a fourth lens group G4having a negative refractive power; and a fifth lens group G5 having apositive refractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, a21st lens group G21 having a positive refractive power and a 22nd lensgroup G22 having a positive refractive power. The 21st lens group G21 isconstituted by, in order from the object, a biconvex lens L21 and acemented lens including a negative meniscus lens L22 having a concavesurface oriented toward the image side and a positive meniscus lens L23having a convex surface oriented toward the object side. The 22nd lensgroup G22 is constituted by a cemented lens including, in order from theobject, a biconvex lens L24 and a negative meniscus lens L25 having aconcave surface oriented toward the object side.

The third lens group G3 is constituted by, in order from the object, anegative meniscus lens L31 having a concave surface oriented toward theobject side and a biconvex lens L32. The biconvex lens L32 has anaspherical image-side surface.

The fourth lens group G4 is constituted by a cemented lens including, inorder from the object, a biconcave lens L41 and a positive meniscus lensL42 having a convex surface oriented toward the object side. Thepositive meniscus lens L42 has an aspherical image-side surface.

The fifth lens group G5 is constituted by, in order from the object, abiconvex lens L51, a cemented lens including a biconvex lens L52 and anegative meniscus lens L53 having a concave surface oriented toward theobject side, and a cemented lens including a biconvex lens L54 and abiconcave lens L55. The biconvex lens L52 has an aspherical object-sidesurface. The biconcave lens L55 has an aspherical image-side surface.

An aperture stop S is provided between the second lens group G2 and thethird lens group G3, and the aperture stop S forms the third lens groupG3.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by moving the first lens group G1 toward the imageside and then moving the same toward the object side, moving the secondlens group G2 toward the object side, moving the third lens group G3toward the object side, fixing the fourth lens group G4 in relation tothe image plane, and moving the fifth lens group G5 toward the objectside such that the distances between the respective lens groups arechanged. The aperture stop S is moved toward the object side integrallywith the third lens group G3.

Focusing from an object at infinity to an object at a close distance isperformed by moving the 21st lens group G21 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the fourth lens group G4 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K.

In Example 5, in the wide-angle end state, since the vibration reductioncoefficient is −1.03 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.23 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −1.12 and the focallength is 23.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.68° is −0.25 mm. In thetelephoto end state, since the vibration reduction coefficient is −1.37and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.24 mm.

Table 5 illustrates the values of respective specifications of Example5. Surface numbers 1 to 32 in Table 5 correspond to optical surfaces ofm1 to m32 illustrated in FIG. 17 .

TABLE 5 [Lens Specification] Surface number R D nd νd *1 207.85739 3.0001.76690 46.9 *2 16.71640 12.075  1.00000 *3 −126.64950 1.700 1.7669046.9 4 138.69829 1.900 1.00000 5 −305.30737 1.700 1.49700 81.7 649.66923 1.200 1.00000 7 48.16519 5.621 1.75520 27.6 8 −201.97549 (D8) 1.00000 9 42.04729 8.608 1.64769 33.7 10 −374.37994 0.100 1.00000 1149.19749 1.000 1.84666 23.8 12 19.13552 4.835 1.60342 38.0 13 51.73593(D13) 1.00000 14 46.66560 6.999 1.49700 81.7 15 −31.81612 1.400 1.8466623.8 16 −46.26169 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18−41.32099 1.300 1.90366 31.3 19 −114.37285 0.100 1.00000 20 118.371753.171 1.84666 23.8 *21 −71.92314 (D21) 1.00000 22 −71.28950 1.3001.80400 46.6 23 28.48969 3.132 1.80518 25.4 *24 57.82940 (D24) 1.0000025 32.18491 7.336 1.49700 81.7 26 −48.06359 0.100 1.00000 *27 101.549118.015 1.49700 81.7 28 −28.00000 1.500 1.74950 35.2 29 −184.91003 0.5001.00000 30 50.32451 6.043 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0*32 136.26267 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 1.94090e−06 −1.49023e−09 −3.81067e−12   6.84376e−15 20.00000e+00 6.00339e−06  2.07998e−09 7.93413e−11 −2.62472e−13 31.00000e+00 −3.68171e−06  −3.47017e−09 4.98784e−11 −2.14759e−13 211.00000e+00 2.76768e−06 −5.47451e−09 1.50258e−11 −4.82676e−14 241.00000e+00 −4.45941e−06   2.05441e−09 2.73993e−11 −5.84691e−14 271.00000e+00 1.45862e−06 −4.94280e−09 −2.35002e−11   5.70437e−14 321.00000e+00 1.61827e−05  1.00472e−08 −2.91720e−11   1.40466e−13 [VariousData] W M T f 16.40 23.50 34.00 FNo 2.81 2.81 2.87 ω 54.1 39.5 29.0 Y20.00 20.00 20.00 TL 163.819 160.497 163.297 BF 25.292 29.551 37.861[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 336.18 339.50 336.70 β — — — −0.0457 −0.0652 −0.0954f 16.40 23.50 34.00 — — — D8 25.802 11.237 2.000 27.363 12.989 4.002 D136.063 6.063 6.063 4.502 4.311 4.061 D16 3.000 11.092 19.651 3.000 11.09219.651 D21 2.000 5.157 8.625 2.000 5.157 8.625 D24 13.764 9.499 1.20013.764 9.499 1.200 D32 25.292 29.551 37.861 25.292 29.551 37.861 [LensGroup Data] Lens group Starting surface Focal distance 1st lens group 1−23.00 2nd lens group 9 40.81 21st lens group 9 86.19 22nd lens group 1456.83 3rd lens group 17 181.29 4th lens group 22 −39.15 5th lens group25 37.83 [Conditional Expression Correspondence Values] ConditionalExpression (5) (D34T − D34W)/(D23T − D23W) = 0.398 ConditionalExpression (6) f4/f3 = −0.216 Conditional Expression (7) f1/f4 = 0.588Conditional Expression (8) A(T3.5)/A(T4.0) = 1.714 (A(T3.5) = −0.0169,A(T4.0) = −0.0099)

It can be understood from Table 5 that the variable magnificationoptical system ZL3 according to Example 5 satisfies ConditionalExpressions (5) to (8).

FIG. 18 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL3 according to Example 5, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 19 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL3 according to Example 5, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 20shows graphs illustrating lateral aberration of the variablemagnification optical system ZL3 according to Example 5 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

It can be understood from FIGS. 18 to 20 that the variable magnificationoptical system ZL3 according to Example 5 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL3 has an excellent imagingperformance upon image blur correction.

According to the above-described examples, it is possible to implement avariable magnification optical system which has a bright F-value ofapproximately F2.8 and such a wide angle of view that the half-angle ofview is approximately 50° or more, and in which various aberrations arecorrected satisfactorily.

While the present invention has been described by assigning referencesymbols to elements of the embodiment for better understanding of thepresent invention, the aspect of the present invention is not limited tothis. The following content can be appropriately employed within a rangewhere the optical performance of the variable magnification opticalsystem is not diminished.

Although the numbered examples of a five-group configuration have beenillustrated as numbered examples of the variable magnification opticalsystem ZL, the present invention is not limited to this and can beapplied to other group configurations (for example, a six-groupconfiguration or the like). Specifically, a configuration in which alens or a lens group is added to the side closest to the object side anda configuration in which a lens or a lens group is added to the sideclosest to the image side may be employed. The first lens group G1 maybe divided into a plurality of lens groups, and the respective lensgroups may be moved along different trajectories upon varyingmagnification or one of them may be fixed. Moreover, as described above,the third lens group G3 may have a negative refractive power or apositive refractive power. A lens group refers to a portion having atleast one lens isolated by air space which changes upon varyingmagnification or focusing.

In the variable magnification optical system ZL, a portion of a lensgroup, an entire lens group, or a plurality of lens groups may be movedin the optical axis direction as a focusing lens group in order toperform focusing from an object at infinity to an object at a closedistance. Moreover, such a focusing lens group can be applied toautofocus and is also suitable for driving based on an autofocus motor(for example, an ultrasonic motor, a step motor, a voice coil motor, orthe like). In particular, although it is preferable that a portion ofthe second lens group G2 be configured as a focusing lens group, theentire second lens group G2 may be configured as a focusing lens group.Moreover, although the focusing lens group may include one single lensand one cemented lens described above, the number of lenses is notparticularly limited and the focusing lens group may include one or morelens components.

In the variable magnification optical system ZL, an entire arbitrarylens group or a partial lens group may be moved so as to have acomponent in the direction orthogonal to the optical axis or may berotated (oscillated) in an in-plane direction including the optical axisso as to function as a vibration-reduction lens group that correctsimage blur occurring due to camera shake or the like. As describedabove, although it is preferable that the entire fourth lens group G4 beconfigured as a vibration-reduction lens group, a portion of the fourthlens group G4 may be configured as a vibration-reduction lens group.Moreover, although the vibration-reduction lens group may be constitutedby one cemented lens as described above, the number of lenses is notparticularly limited and the vibration-reduction lens group may beconstituted by one single lens or a plurality of lens components.Moreover, the vibration-reduction lens group may have a positiverefractive power and it is preferable that the entire fourth lens groupG4 have a negative refractive power.

In the variable magnification optical system ZL, the lens surface may beformed as a spherical surface or a flat surface and may be formed as anaspherical surface. When the lens surface is a spherical surface or aflat surface, it is possible to facilitate lens processing, assembly,and adjustment and to prevent deterioration of optical performanceresulting from errors in the processing, assembly and adjustment.Moreover, deterioration of the rendering performance is little even whenthe image plane is shifted. When the lens surface is an asphericalsurface, the aspherical surface may be an aspherical surface obtained bygrinding a glass-molded aspherical surface obtained by molding glassinto an aspherical surface, or a composite aspherical surface obtainedby forming a resin on the surface of glass into an aspherical shape.Moreover, the lens surface may be a diffraction surface and may be arefractive index distributed lens (a GRIN lens) or a plastic lens.

In the variable magnification optical system ZL, it is preferable thatthe aperture stop S be disposed in the third lens group G3 so as to beintegrated with the third lens group G3 particularly. However, theaperture stop S may be configured so as to be movable separately fromthe third lens group G3. Moreover, the role of the aperture stop may besubstituted by the frame of a lens without providing a separate memberas the aperture stop.

In the variable magnification optical system ZL, each lens surface maybe coated with an anti-reflection film which has high transmittance in awide wavelength region in order to decrease flare and ghosting andachieve satisfactory optical performance with high contrast. The type ofthe anti-reflection film may be selected appropriately. Moreover, thenumber of anti-reflection films and the position thereof may be selectedappropriately. In the above-described examples, it is preferable thatany one of the image-side surface of the lens L11, the object-sidesurface of the lens L12, the image-side surface of the lens L12, theobject-side surface of the lens L13, the image-side surface of the lensL13, and the object-side surface of the lens L14 of the first lens groupG1 or a plurality of surfaces be coated with anti-reflection film whichhas high transmittance in a wavelength region.

The variable magnification ratio of the variable magnification opticalsystem ZL may be between approximately 1.5 and 2.5, for example.Moreover, the focal length (a value converted in terms of a 35-mm thickplate) in the wide-angle end state of the variable magnification opticalsystem ZL may be between approximately 15 and 20 mm, for example.Moreover, the F-value in the wide-angle end state of the variablemagnification optical system ZL may be between approximately 2.7 and3.5, for example. Moreover, the F-value in the telephoto end state ofthe variable magnification optical system ZL may be betweenapproximately 2.7 and 3.5, for example. Furthermore, when the focusingstate of the variable magnification optical system ZL changes from thewide-angle end state to the telephoto end state, the F-value may beapproximately constant (a variation is equal to or smaller than 10percent of the F-value in the telephoto end state).

Another embodiment will now be described with reference to the drawings.FIG. 21 illustrates an example of a configuration of a variablemagnification optical system ZL. In other examples, the number of lensgroups, a lens configuration of each lens group, and the like can bechanged appropriately.

In an embodiment, a variable magnification optical system includes, inorder from an object, a first lens group G1 having a negative refractivepower, a second lens group G2 having a positive refractive power, athird lens group G3 having a positive refractive power, a fourth lensgroup G4, a fifth lens group G5 having a negative refractive power, anda sixth lens group G6 having a positive refractive power, the systemperforming varying magnification by changing the distance between thefirst and second lens groups G1 and G2, the distance between the secondand third lens groups G2 and G3, the distance between the third andfourth lens groups G3 and G4, the distance between the fourth and fifthlens groups G4 and G5, and the distance between the fifth and sixth lensgroups G5 and G6, and at least a portion of any one lens group among thefirst to sixth lens groups G1 to G6 is configured to be movable so as tohave a component in the direction orthogonal to an optical axis.

Alternatively, a variable magnification optical system ZL includes, inorder from an object, a first lens group G1 having a negative refractivepower, a second lens group G2 having a positive refractive power, athird lens group G3 having a positive refractive power, a fourth lensgroup G4, a fifth lens group G5 having a negative refractive power, anda sixth lens group G6 having a positive refractive power, the systemperforming varying magnification by changing the distances between therespective lens groups, and at least a portion of any one lens groupamong the first to sixth lens groups G1 to G6 may be configured to bemovable so as to have a component in the direction orthogonal to anoptical axis in order to correct image blur as a vibration-reductionlens group VR.

The variable magnification optical system has the first lens group G1having a negative refractive power, the second lens group G2 having apositive refractive power, the third lens group G3 having a positiverefractive power, the fourth lens group G4, the fifth lens group G5having a negative refractive power, and the sixth lens group G6 having apositive refractive power and changes the distances between therespective lens groups. Therefore, it is possible to secure the degreeof freedom in aberration correction and to implement a bright variablemagnification optical system having a wide angle of view. Moreover, atleast a portion of any one lens group among the first to sixth lensgroups G1 to G6 is moved so as to have a component in the directionorthogonal to the optical axis to perform image blur correction.Therefore, it is possible to suppress the occurrence of eccentric comaaberration and one-sided blur during image blur correction and to obtainsatisfactory imaging performance.

The fourth lens group G4 may have a positive refractive power or anegative refractive power.

In the variable magnification optical system ZL, it is preferable thatat least a portion of the fifth lens group G5 be configured to bemovable so as to have a component in the direction orthogonal to theoptical axis in order to correct image blur as a vibration-reductionlens group VR.

When the fifth lens group G5 having a negative refractive power isselected as a lens group (a vibration-reduction lens group VR) that ismoved to perform image blur correction, it is possible to suppress theoccurrence of eccentric aberration (particularly, eccentric comaaberration and eccentric image plane tilting (one-sided blur)) occurringwhen the fifth lens group G5 is shifted eccentrically and to obtainsatisfactory imaging performance during image blur correction. Moreover,the fifth lens group G5 can be constituted by lenses having a relativelysmall lens diameter, and it is possible to effectively decrease the sizeof an image blur correction mechanism and the entire lens.

The fifth lens group G5 may include one or more lenses which areimmovable during image blur correction in addition to thevibration-reduction lens group VR.

The variable magnification optical system ZL satisfies ConditionalExpression (9) below.−0.500<f5/f4<0.500  (9)

where

f5: a focal length of the fifth lens group G5

f4: a focal length of the fourth lens group G4

Conditional Expression (9) is a conditional expression for defining anappropriate value of the focal length of the fifth lens group G5 withrespect to the focal length of the fourth lens group G4. WhenConditional Expression (9) is satisfied, it is possible to set anappropriate moving distance of the fifth lens group G5 for image blurcorrection while correcting eccentric aberration when the fifth lensgroup G5 is shifted eccentrically during image blur correction.

If the focal length ratio exceeds the upper limit value of ConditionalExpression (9), the negative focal length of the fourth lens group G4 isdecreased, aberration correction balance in combination with theadjacent fifth lens group G5 for image blur correction collapses, and itis difficult to secure imaging performance during image blur correction.Moreover, since the focal length of the fifth lens group G5 is increasedtoward the negative side, the moving distance of the fifth lens group G5for image blur correction increases, and the sizes of the image blurcorrection mechanism and the entire lens are increased undesirably.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (9) be set to 0.400. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (9) be set to 0.350.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (9), the positive focal length of the fourth lensgroup G4 is decreased, aberration correction balance in combination withthe adjacent fifth lens group G5 for image blur correction collapses,and it is difficult to secure imaging performance during image blurcorrection. Moreover, since the focal length of the fifth lens group G5is increased toward the negative side, the moving distance of the fifthlens group G5 for image blur correction increases, and the sizes of theimage blur correction mechanism and the entire lens are increasedundesirably.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (9) be set to −0.400. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (9) be set to −0.300.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (10) below.0.300<(−f1)/f6<0.900  (10)

where

f1: a focal length of the first lens group G1

f6: a focal length of the sixth lens group G6

Conditional Expression (10) is a conditional expression for defining thefocal length of the first lens group G1 with respect to the sixth lensgroup G6. When Conditional Expression (10) is satisfied, it is possibleto satisfactorily correct curvature of field and coma aberration whileobtaining a wide angle of view (a half-angle of view of approximately50° or more) in the wide-angle end state.

If the focal length ratio exceeds the upper limit value of ConditionalExpression (10), the negative focal length of the first lens group G1 isincreased, and it is difficult to obtain a wide angle of view (ahalf-angle of view of approximately 50° or more) in the wide-angle endstate. In some cases, the effective diameter of the first lens group G1is increased and the entire lens size is increased undesirably.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (10) be set to 0.800. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (10) be set to 0.700.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (10), the negative focal length of the first lensgroup G1 is decreased, astigmatism and coma aberration in the wide-angleend state are aggravated, and it is difficult to correct theseaberrations.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (10) be set to 0.400. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (10) be set to 0.500.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (11) below.−0.400<f1/f4<0.400  (11)

where

f1: a focal length of the first lens group G1

f4: a focal length of the fourth lens group G4

Conditional Expression (11) is a conditional expression for defining thefocal length of the first lens group G1 with respect to the fourth lensgroup G4. More specifically, Conditional Expression (11) is aconditional expression for defining the focal length of the fourth lensgroup G4 appropriate for correcting eccentric aberration when theadjacent fifth lens group G5 is shifted eccentrically in order toperform image blur correction and the focal length of the first lensgroup G1 for decreasing the entire lens size while obtaining a wideangle of view (a half-angle of view of approximately 50° or more) in thewide-angle end state.

If the focal length ratio exceeds the upper limit value of ConditionalExpression (11), the negative focal length of the fourth lens group G4is decreased, aberration correction balance in combination with theadjacent fifth lens group G5 for image blur correction collapses, and itis difficult to secure imaging performance during image blur correction.In some cases, the negative focal length of the first lens group G1 isincreased, and it is difficult to obtain a wide angle of view (ahalf-angle of view of approximately 50° or more) in the wide-angle endstate. In some cases, the effective diameter of the first lens group G1is increased and the entire lens size is increased undesirably.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (11) be set to 0.300. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (11) be set to 0.200.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (11), the negative focal length of the fourthlens group G4 is decreased, aberration correction balance in combinationwith the adjacent fifth lens group G5 for image blur correctioncollapses, and it is difficult to secure imaging performance duringimage blur correction. In some cases, the negative focal length of thefirst lens group G1 is increased, and it is difficult to obtain a wideangle of view (a half-angle of view of approximately 50° or more) in thewide-angle end state. In some cases, the effective diameter of the firstlens group G1 is increased and the entire lens size is increasedundesirably.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (11) be set to −0.300. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (11) be set to −0.200.

In the variable magnification optical system ZL, it is preferable thatthe fourth lens group G4 have a negative lens and a positive lens.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the fifth lens groupG5 is moved to perform image blur correction. Moreover, it is possibleto effectively correct various aberrations including sphericalaberration and astigmatism upon varying magnification.

In the variable magnification optical system ZL, it is preferable thatthe fifth lens group G5 be constituted by a cemented lens including apositive lens and a negative lens.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the fifth lens groupG5 is moved to perform image blur correction. Moreover, it is possibleto decrease the size and the weight of a lens that moves for image blurcorrection and to effectively decrease the size and the cost of an imageblur correction mechanism.

The fifth lens group G5 may include two lenses (separated from a bondingsurface) instead of bonding a positive lens and a negative lens asdescribed above.

In the variable magnification optical system ZL, it is preferable thatthe lens surface closest to an image, of the fifth lens group G5 be anaspherical surface.

According to this configuration, it is possible to effectively correcteccentric coma aberration and one-sided blur when the fifth lens groupG5 is moved to perform image blur correction.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (12) below.1.100<A(T3.5)/A(T4.0)<5.000  (12)

where

A(T3.5): an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 3.5 passes through the aspherical surface ina telephoto end state

A(T4.0): an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 4.0 passes through the aspherical surface ina telephoto end state

The asphericity refers to an amount of sag, with respect to anapproximately spherical surface, in the aspherical surface along theoptical axis.

Conditional Expression (12) is a Conditional Expression for defining anappropriate value of the asphericity of the aspherical surface closestto an image, of the fifth lens group G5. When Conditional Expression(12) is satisfied, it is possible to satisfactorily correct one-sidedblur and eccentric coma aberration when the fifth lens group G5 is movedto perform image blur correction.

When the asphericity ratio exceeds the upper limit value of ConditionalExpression (12), the asphericity of the fifth lens group G5 becomes toolarge and it is difficult to correct one-sided blur and eccentric comaaberration when the fifth lens group G5 is moved to perform image blurcorrection.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (12) be set to 4.000. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (12) be set to 3.000.

When the asphericity ratio is smaller than the lower limit value ofConditional Expression (12), the asphericity of the fifth lens group G5is insufficient and it is difficult to correct one-sided blur andeccentric coma aberration when the fifth lens group G5 is moved toperform image blur correction.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (12) be set to 1.250. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (12) be set to 1.400.

In the variable magnification optical system ZL, it is preferable thatthe first lens group G1 be immovable in relation to the image plane uponvarying magnification.

According to this configuration, it is possible to effectively simplifya varying magnification mechanism and to increase the durability of alens barrel.

In the variable magnification optical system ZL, it is preferable thatthe fourth lens group G4 be immovable in relation to the image planeupon varying magnification.

According to this configuration, it is possible to simplify a varyingmagnification mechanism and to effectively decrease the size and thecost and to secure an imaging performance due to a reduced eccentricerror. Moreover, this effect is significant when a diaphragm isintegrated with the fourth lens group G4.

In the variable magnification optical system ZL, it is preferable thatthe fifth lens group G5 be immovable in relation to the image plane uponvarying magnification.

According to this configuration, it is possible to simplify a varyingmagnification mechanism and to effectively decrease the size and thecost. Particularly, when the fifth lens group G5 is used as avibration-reduction lens group VR, it is not necessary to move an imageblur correction mechanism in the optical axis direction and it ispossible to particularly effectively reduce the entire lens size.

In the variable magnification optical system ZL, it is preferable thatfocusing be performed by moving at least a portion of any one lens groupamong the second to sixth lens groups G2 to G6 in the optical axisdirection as a focusing lens group.

According to this configuration, since a lens group other than the firstlens group G1 which is large and heavy is used as a focusing lens group,it is possible to reduce the size and the weight of the focusing lensgroup and to increase a focusing speed.

In the variable magnification optical system ZL, it is preferable thatfocusing be performed by moving the second lens group G2 in the opticalaxis direction as a focusing lens group.

According to this configuration, it is possible to decrease the size andthe weight of a focusing lens group and to reliably increase a focusingspeed. Moreover, the moving distance for focusing in the wide-angle endstate can be controlled to be approximately equal to that in thewide-angle end state, and a focusing error when varying magnification isperformed upon focusing on an object at a close point can be reduced.

Preferably, the variable magnification optical system ZL satisfiesConditional Expression (13) below.0.500<f2/f3<2.000  (13)

where

f2: a focal length of the second lens group G2

f3: a focal length of the third lens group G3

Conditional Expression (13) is a conditional expression for defining anappropriate focal length ratio between the second and third lens groupsG2 and G3 when focusing is performed using the second lens group G2.When Conditional Expression (13) is satisfied, it is possible todecrease a difference in a focusing moving distance between in thewide-angle end state and the telephoto end state.

When the focal length ratio exceeds the upper limit value of ConditionalExpression (13), the focal length of the second lens group G2 isincreased and the focusing moving distance is increased. Due to this,the focusing mechanism becomes complex and the focusing speed isdecreased. Particularly, the focusing moving distance in the telephotoend state is increased and a focusing error when varying magnificationis performed upon focusing on an object at a close point is increasedundesirably.

In order to obtain the effect reliably, it is preferable that the upperlimit value of Conditional Expression (13) be set to 1.900. In order toobtain the effect more reliably, it is preferable that the upper limitvalue of Conditional Expression (13) be set to 1.800.

If the focal length ratio is smaller than the lower limit value ofConditional Expression (13), the focal length of the second lens groupG2 is decreased and the focusing moving distance in the wide-angle endstate is increased. Due to this, a difference in a focusing movingdistance between in the wide-angle end state and the telephoto end stateis increased, and a focusing error when varying magnification isperformed upon focusing on an object at a close point is increasedundesirably.

In order to obtain the effect reliably, it is preferable that the lowerlimit value of Conditional Expression (13) be set to 0.700. In order toobtain the effect more reliably, it is preferable that the lower limitvalue of Conditional Expression (13) be set to 0.900.

In this way, it is possible to implement the variable magnificationoptical system ZL which has a bright F-value and a wide angle of viewand in which various aberrations are corrected satisfactorily.

The above-described variable magnification optical system ZL may beincluded in the camera (an optical apparatus) illustrated in FIG. 33 .

As can be understood from respective examples to be described later, thevariable magnification optical system ZL mounted on the camera 1 as theimage capturing lens 2 has a bright F-value and a wide angle of view andhas a satisfactory optical performance such that various aberrations arecorrected satisfactorily due to its characteristic lens configuration.Therefore, according to the camera 1, it is possible to implement anoptical apparatus which has a bright F-value and a wide angle of viewand has a satisfactory optical performance such that various aberrationsare corrected satisfactorily.

Although a mirrorless camera has been described as an example of thecamera 1, the camera is not limited to this. For example, the sameeffect as the camera 1 can be obtained even when the above-describedvariable magnification optical system ZL is mounted on a single-lensreflex camera which has a quick return mirror on a camera body and viewsa subject using a finder optical system.

Next, an example of a method for manufacturing the above-describedvariable magnification optical system ZL will be described. FIGS. 38 and39 illustrate an example of a method for manufacturing the variablemagnification optical system ZL.

In the example illustrated in FIG. 38 , first, respective lensesincluding a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a positive refractive power; a fourth lens group G4; afifth lens group G5 having a negative refractive power; and a sixth lensgroup G6 having a positive refractive power are arranged, in order fromthe object, in a lens barrel such that varying magnification isperformed by changing the distance between the first and second lensgroups G1 and G2, the distance between the second and third lens groupsG2 and G3, the distance between the third and fourth lens groups G3 andG4, the distance between the fourth and fifth lens groups G4 and G5, andthe distance between the fifth and sixth lens groups G5 and G6 (stepST1). The respective lenses are arranged such that at least a portion ofany one lens group among the first to sixth lens groups G1 to G6 isconfigured to be movable so as to have a component in the directionorthogonal to the optical axis (step ST2).

In the example illustrated in FIG. 39 , first, respective lensesincluding a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a positive refractive power; a fourth lens group G4; afifth lens group G5 having a negative refractive power; and a sixth lensgroup G6 having a positive refractive power are arranged, in order fromthe object, in a lens barrel such that varying magnification isperformed by changing the distances between the respective lens groups(step ST10). The respective lenses are arranged such that at least aportion of any one lens group among the first to sixth lens groups G1 toG6 is configured to be movable so as to have a component in thedirection orthogonal to the optical axis in order to correct image blur(step ST20).

According to an example of a lens arrangement, as illustrated in FIG. 21, a negative meniscus lens L11 having a concave surface oriented towardan image side, a biconcave lens L12, a biconcave lens L13, and abiconvex lens L14 are arranged, in order from the object, to form thefirst lens group G1. A biconvex lens L21 and a cemented lens including anegative meniscus lens L22 having a concave surface oriented toward theimage side and a positive meniscus lens L23 having a convex surfaceoriented toward the object side are arranged, in order from the object,to form the second lens group G2. A cemented lens including a biconvexlens L31 and a negative meniscus lens L32 having a concave surfaceoriented toward the object side arranged in order from the object formsthe third lens group G3. A biconcave lens L41 and a biconvex lens L42are arranged, in order from the object, to form the fourth lens groupG4. A cemented lens including a biconcave lens L51 and a positivemeniscus lens L52 having a convex surface oriented toward the objectside arranged in order from the object forms the fifth lens group G5. Abiconvex lens L61, a cemented lens including a biconvex lens L62 and abiconcave lens L63, and a cemented lens including a biconvex lens L64and a biconcave lens L65 are arranged, in order from the object, to formthe sixth lens group G6. The respective lens groups prepared in thismanner are arranged in the above-described order to manufacture thevariable magnification optical system ZL.

According to the above-described manufacturing method, it is possible tomanufacture the variable magnification optical system ZL which has abright F-value and a wide angle of view and in which various aberrationsare corrected satisfactorily.

Hereinafter, respective examples will be described with reference to thedrawings.

FIGS. 21, 25, and 29 are cross-sectional views illustrating theconfiguration and the refractive power allocation of variablemagnification optical systems ZL (ZL1 to ZL3) according to respectiveexamples. In the lower part of the cross-sectional views of the variablemagnification optical systems ZL1 to ZL3, the moving directions alongthe optical axis of each lens group upon varying magnification from thewide-angle end state (W) to the telephoto end state (T) via theintermediate focal length state (M) are indicated by arrows. In theupper part of the cross-sectional views of the variable magnificationoptical systems ZL1 to ZL3, the moving direction of the focusing lensgroup upon focusing from an object at infinity to an object at a closedistance is indicated by an arrow and the state of thevibration-reduction lens group VR when correcting image blur is alsoillustrated.

Respective reference symbols in FIG. 21 associated with Example 6 areused independently in respective examples in order to avoid complicationof description due to an increased number of reference symbolcharacters. Therefore, even when components in diagrams associated withother examples are denoted by the same reference symbols as used in FIG.21 , these components do not necessarily have the same configuration asthose of other examples.

Tables 6 to 8 illustrated below are tables of respective specificationsof Examples 6 to 8.

In the respective examples, the d-line (wavelength: 587.562 nm) and theg-line (wavelength: 435.835 nm) are selected as an aberrationcharacteristics calculation target.

In [Lens Specification] in tables, a surface number indicates a sequencenumber of an optical surface from an object side along a travelingdirection of light, R indicates a radius of curvature of each opticalsurface, D indicates a surface distance which is the distance on theoptical axis from each optical surface to the next optical surface (oran image plane), nd indicates a refractive index for the d-line, of amaterial of an optical member, and vd indicates the Abbe number for thed-line, of a material of an optical member. Moreover, Di indicates asurface distance between an i-th surface and an (i+1)th surface andAperture stop indicates an aperture stop S. When the optical surface isan aspherical surface, a mark “*” is assigned to the surface number anda paraxial radius of curvature is shown in the radius of curvaturecolumn R.

In [Aspheric Data] in tables, the shape of an aspherical surface shownin [Lens Specification] is expressed by Equation (a) below. X(y)indicates the distance along the optical axis direction from atangential plane at the vertex of an aspherical surface to a position onthe aspherical surface at a height y, R indicates a radius of curvature(a paraxial radius of curvature) of a reference spherical surface, κindicates a conic constant, and Ai indicates an aspheric coefficient atdegree i. “E-n” indicates “×10⁻¹¹”. For example, 1.234E-05=1.234×10⁻⁵.An aspheric coefficient A2 at degree 2 is 0 and is not illustrated.X(y)=(y ² /R)/{1+(1−κ×y ² /R ²)^(1/2) }±A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y¹⁰  (a)

In [Various Data] in tables, f indicates a focal length of an entirelens system, FNo indicates the F-number, ω indicates a half-angle ofview (unit: °), Y indicates the maximum image height, BF indicates thedistance (an air-conversion length) from the last lens surface to theimage plane I on the optical axis upon focusing on an object atinfinity, and TL indicates the sum of BF and the distance from thefrontmost lens surface to the last lens surface on the optical axis uponfocusing on an object at infinity.

In [Variable Distance Data] in tables, Di indicates a surface distancebetween an i-th surface and an (i+1)th surface, D0 indicates an axialair distance between an object plane and a lens surface closest to anobject, of the first lens group G1, f indicates the focal length of anentire lens system, and β indicates an imaging magnification.

In [Lens Group Data] in tables, the starting surface and the focallength of the lens groups are shown.

In [Conditional Expression Correspondence Values] in tables, valuescorresponding to Conditional Expressions (9) to (13) are illustrated.

Hereinafter, “mm” is generally used as the unit of the focal length f,the radius of curvature R, the surface distance D, and other lengths andthe like described in all specification values unless particularlystated otherwise. However, the unit is not limited to this since anequivalent optical performance is obtained even when the optical systemis proportionally expanded or reduced. Moreover, the unit is not limitedto “mm” and other appropriate units may be used.

The above description of tables is common to all examples, anddescription thereof will not be provided below.

Example 6

Example 6 will be described with reference to FIGS. 21 to 24 and Table6. As illustrated in FIG. 21 , a variable magnification optical systemZL (ZL1) according to Example 6 is constituted by, in order from anobject, a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a positive refractive power; a fourth lens group G4having a negative refractive power; a fifth lens group G5 having anegative refractive power; and a sixth lens group G6 having a positiverefractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, abiconvex lens L21 and a cemented lens including a negative meniscus lensL22 having a concave surface oriented toward the image side and apositive meniscus lens L23 having a convex surface oriented toward theobject side.

The third lens group G3 is constituted by a cemented lens including, inorder from the object, a biconvex lens L31 and a negative meniscus lensL32 having a concave surface oriented toward the object side.

The fourth lens group G4 is constituted by, in order from the object, abiconcave lens L41 and a biconvex lens L42.

The fifth lens group G5 is constituted by a cemented lens including, inorder from the object, a biconcave lens L51 and a positive meniscus lensL52 having a convex surface oriented toward the object side. Thepositive meniscus lens L52 has an aspherical image-side surface.

The sixth lens group G6 is constituted by, in order from the object, abiconvex lens L61, a cemented lens including a biconvex lens L62 and abiconcave lens L63, and a cemented lens including a biconvex lens L64and a biconcave lens L65. The biconcave lens L65 has an asphericalimage-side surface.

An aperture stop S is provided between the third lens group G3 and thefourth lens group G4, and the aperture stop S forms the fourth lensgroup G4.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by moving the first lens group G1 toward the imageside and moving the same toward the object side, moving the second lensgroup G2 toward the object side, moving the third lens group G3 towardthe object side, moving the fourth lens group G4 toward the object side,moving the fifth lens group G5 toward the object side, and moving thesixth lens group G6 toward the object side such that the distancesbetween the respective lens groups (the distance between the first andsecond lens groups G1 and G2, the distance between the second and thirdlens groups G2 and G3, the distance between the third and fourth lensgroups G3 and G4, the distance between the fourth and fifth lens groupsG4 and G5, and the distance between the fifth and sixth lens groups G5and G6) are changed. The aperture stop S is moved toward the object sideintegrally with the fourth lens group G4.

Focusing from an object at infinity to an object at a close distance isperformed by moving the second lens group G2 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the fifth lens group G5 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K.

In Example 6, in the wide-angle end state, since the vibration reductioncoefficient is −0.64 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.36 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −0.76 and the focallength is 23.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.68° is −0.36 mm. In thetelephoto end state, since the vibration reduction coefficient is −0.93and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.36 mm.

Table 6 illustrates the values of respective specifications of Example6. Surface numbers 1 to 32 in Table 6 correspond to optical surfaces ofm1 to m32 illustrated in FIG. 21 .

TABLE 6 [Lens Specification] Surface number R D nd νd *1 151.57543 3.0001.76690 46.9 *2 16.71640 11.694  1.00000 *3 −185.40568 1.700 1.7669046.9 4 99.91509 2.170 1.00000 5 −274.19230 1.700 1.49700 81.7 6 49.100901.360 1.00000 7 48.81906 5.099 1.75520 27.6 8 −219.36815 (D8)  1.00000 946.26831 4.082 1.64769 33.7 10 −187.68256 0.100 1.00000 11 56.375311.000 1.84666 23.8 12 19.88291 4.835 1.60342 38.0 13 62.23978 (D13)1.00000 14 50.91403 6.157 1.49700 81.7 15 −37.11951 1.400 1.84666 23.816 −49.12403 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18 −37.348481.300 1.90366 31.3 19 339.67895 1.232 1.00000 20 109.52156 3.549 1.8466623.8 21 −57.24803 (D21) 1.00000 22 −96.39093 1.300 1.80400 46.6 2333.70480 3.529 1.80518 25.4 *24 130.78415 (D24) 1.00000 25 30.941697.448 1.49700 81.7 26 −51.16421 0.100 1.00000 27 51.26380 7.685 1.4970081.7 28 −28.22102 1.500 1.74950 35.2 29 70.36935 1.879 1.00000 3044.36240 6.229 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0 *328552.25410 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 1.52765e−06 −2.32063e−09 −3.31568e−12   6.28041e−15 20.00000e+00 8.58810e−06 −3.90468e−10 8.78796e−11 −3.06104e−13 31.00000e+00 −2.38304e−06   2.33737e−10 4.37038e−11 −1.95636e−13 241.00000e+00 −1.34495e−06  −1.30741e−09 1.88294e−11 −4.98252e−14 321.00000e+00 1.59358e−05  1.01734e−08 8.62033e−12  3.21603e−14 [VariousData] W M T f 16.40 23.50 34.00 FNo 2.88 2.88 2.93 ω 54.0 40.5 29.6 Y20.00 20.00 20.00 TL 163.818 161.015 162.021 BF 26.430 35.126 45.401[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 336.18 338.99 337.98 β — — — −0.0457 −0.0652 −0.0949f 16.40 23.50 34.00 — — — D8 25.987 9.457 2.038 27.527 11.210 3.979 D137.006 12.655 5.930 5.466 10.902 3.989 D16 3.000 9.141 20.142 3.000 9.14120.142 D21 2.000 3.664 2.000 2.000 3.664 2.000 D24 14.086 5.661 1.20014.086 5.661 1.200 D32 26.430 35.126 45.401 26.430 35.126 45.401 [LensGroup Data] Lens group Starting surface Focal distance 1st lens group 1−22.97 2nd lens group 9 85.91 3rd lens group 14 57.96 4th lens group 17−366.64 5th lens group 22 −68.50 6th lens group 25 41.25 [ConditionalExpression Correspondence Values] Conditional Expression (9) f5/f4 =0.187 Conditional Expression (10) (−f1)/f6 = 0.557 ConditionalExpression (11) f1/f4 = 0.063 Conditional Expression (12)A(T3.5)/A(T4.0) = 1.735 (A(T3.5) = −0.0111, A(T4.0) = −0.0064)Conditional Expression (13) 12/13 = 1.482

It can be understood from Table 6 that the variable magnificationoptical system ZL1 according to Example 6 satisfies ConditionalExpressions (9) to (13).

FIG. 22 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL1 according to Example 6, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 23 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL1 according to Example 6, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 24shows graphs illustrating lateral aberration of the variablemagnification optical system ZL1 according to Example 6 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

In the graphs illustrating respective aberrations, FNO indicates theF-number, NA indicates a numerical aperture, A indicates a half-angle ofview (unit: °) at each image height, and HO indicates an object height.d indicates aberration at the d-line and g indicates aberration at theg-line. Moreover, aberrations without these characters indicateaberrations at the d-line. In the graphs illustrating the sphericalaberration upon focusing on an object at infinity, the F-number valuescorresponding to the maximum aperture are illustrated. In the graphsillustrating the spherical aberration upon focusing on an object at aclose point, the numerical aperture values corresponding to the maximumaperture are illustrated. In the graphs illustrating the astigmatism, asolid line indicates the sagittal image plane and a broken lineindicates the meridional image plane.

The same reference symbols as in this example are used in the aberrationgraphs of respective examples to be described later.

It can be understood from FIGS. 22 to 24 that the variable magnificationoptical system ZL1 according to Example 6 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL1 has an excellent imagingperformance upon image blur correction.

Example 7

Example 7 will be described with reference to FIGS. 25 to 28 and Table7. As illustrated in FIG. 25 , a variable magnification optical systemZL (ZL2) according to Example 7 is constituted by, in order from anobject, a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a positive refractive power; a fourth lens group G4having a negative refractive power; a fifth lens group G5 having anegative refractive power; and a sixth lens group G6 having a positiverefractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, abiconvex lens L21 and a cemented lens including a negative meniscus lensL22 having a concave surface oriented toward the image side and apositive meniscus lens L23 having a convex surface oriented toward theobject side.

The third lens group G3 is constituted by a cemented lens including, inorder from the object, a biconvex lens L31 and a negative meniscus lensL32 having a concave surface oriented toward the object side.

The fourth lens group G4 is constituted by, in order from the object, anegative meniscus lens L41 having a concave surface oriented toward theobject side and a biconvex lens L42.

The fifth lens group G5 is constituted by a cemented lens including, inorder from the object, a biconcave lens L51 and a positive meniscus lensL52 having a convex surface oriented toward the object side. Thepositive meniscus lens L52 has an aspherical image-side surface.

The sixth lens group G6 is constituted by, in order from the object, abiconvex lens L61, a cemented lens including a biconvex lens L62 and abiconcave lens L63, and a cemented lens including a biconvex lens L64and a biconcave lens L65. The biconcave lens L65 has an asphericalimage-side surface.

An aperture stop S is provided between the third lens group G3 and thefourth lens group G4, and the aperture stop S forms the fourth lensgroup G4.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by fixing the first lens group G1 in relation to theimage plane, moving the second lens group G2 toward the object side,moving the third lens group G3 toward the object side, fixing the fourthlens group G4 in relation to the image plane, moving the fifth lensgroup G5 toward the image side and then moving the same toward theobject side, and moving the sixth lens group G6 toward the object sidesuch that the distances between the respective lens groups (the distancebetween the first and second lens groups G1 and G2, the distance betweenthe second and third lens groups G2 and G3, the distance between thethird and fourth lens groups G3 and G4, the distance between the fourthand fifth lens groups G4 and G5, and the distance between the fifth andsixth lens groups G5 and G6) are changed. The aperture stop S is fixedin relation to the image plane integrally with the fourth lens group G4.

Focusing from an object at infinity to an object at a close distance isperformed by moving the second lens group G2 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the fifth lens group G5 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K.

In Example 7, in the wide-angle end state, since the vibration reductioncoefficient is −0.68 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.34 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −0.83 and the focallength is 23.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.68° is −0.34 mm. In thetelephoto end state, since the vibration reduction coefficient is −0.95and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.35 mm.

Table 7 illustrates the values of respective specifications of Example7. Surface numbers 1 to 32 in Table 7 correspond to optical surfaces ofm1 to m32 illustrated in FIG. 25 .

TABLE 7 [Lens Specification] Surface number R D nd νd *1 200.42947 3.0001.76690 46.9 *2 17.07497 11.709  1.00000 *3 −200.00000 1.700 1.7669046.9 4 109.91543 1.900 1.00000 5 −693.49354 1.700 1.49700 81.7 649.25847 1.200 1.00000 7 50.08128 4.923 1.75520 27.6 8 −295.12270 (D8) 1.00000 9 56.93713 4.745 1.64769 33.7 10 −156.65949 0.100 1.00000 1147.36415 1.000 1.84666 23.8 12 21.40251 4.835 1.60342 38.0 13 47.99942(D13) 1.00000 14 45.23118 6.615 1.49700 81.7 15 −36.27556 1.400 1.8466623.8 16 −49.02120 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18−34.76577 1.300 1.90366 31.3 19 −208.11349 0.100 1.00000 20 1901.471903.098 1.84666 23.8 21 −49.48608 (D21) 1.00000 22 −126.18353 1.3001.80400 46.6 23 29.00114 3.536 1.80518 25.4 *24 83.38799 (D24) 1.0000025 32.33148 7.547 1.49700 81.7 26 −47.61976 0.100 1.00000 27 54.518827.863 1.49700 81.7 28 −28.00000 1.500 1.74950 35.2 29 206.04990 0.5001.00000 30 66.17138 6.083 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0*32 861.15398 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 7.17332e−07 5.06827e−10 −3.44033e−12   4.39234e−15 20.00000e+00 2.76313e−06 5.96322e−09 1.96762e−11 −9.83208e−14 31.00000e+00 −3.91032e−06  1.30563e−09 7.32124e−12 −8.19441e−14 241.00000e+00 −1.84007e−06  −1.52537e−09  3.88829e−11 −1.13936e−13 321.00000e+00 1.32449e−05 9.98520e−09 −1.19528e−11   7.08648e−14 [VariousData] W M T f 16.40 23.50 34.00 FNo 2.89 2.89 2.88 ω 54.1 40.7 29.4 Y20.00 20.00 20.00 TL 163.818 163.818 163.818 BF 27.200 36.104 42.239[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 336.18 336.18 336.18 β — — — −0.0457 −0.0658 −0.0954f 16.40 23.50 34.00 — — — D8 26.014 8.000 3.463 27.625 9.934 5.532 D136.348 17.201 6.207 4.737 15.267 4.137 D16 3.000 10.164 25.693 3.00010.164 25.693 D21 3.470 4.520 2.000 3.470 4.520 2.000 D24 14.768 4.8131.200 14.768 4.813 1.200 D32 27.200 36.102 42.239 27.200 36.102 42.239[Lens Group Data] Lens group Starting surface Focal distance 1st lensgroup 1 −23.00 2nd lens group 9 92.82 3rd lens group 14 54.87 4th lensgroup 17 −326.41 5th lens group 22 −61.92 6th lens group 25 38.74[Conditional Expression Correspondence Values] Conditional Expression(9) f5/f4 = 0.190 Conditional Expression (10) (−f1)/f6 = 0.594Conditional Expression (11) f1/f4 = 0.070 Conditional Expression (12)A(T3.5)/A(T4.0) = 1.707 (A(T3.5) = −0.0102, A(T4.0) = −0.0060)Conditional Expression (13) f2/f3 = 1.692

It can be understood from Table 7 that the variable magnificationoptical system ZL2 according to Example 7 satisfies ConditionalExpressions (9) to (13).

FIG. 26 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL2 according to Example 7, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 27 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL2 according to Example 7, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 28shows graphs illustrating lateral aberration of the variablemagnification optical system ZL2 according to Example 7 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

It can be understood from FIGS. 26 to 28 that the variable magnificationoptical system ZL2 according to Example 7 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL2 has an excellent imagingperformance upon image blur correction.

Example 8

Example 8 will be described with reference to FIGS. 29 to 32 and Table8. As illustrated in FIG. 29 , a variable magnification optical systemZL (ZL3) according to Example 8 is constituted by, in order from anobject, a first lens group G1 having a negative refractive power; asecond lens group G2 having a positive refractive power; a third lensgroup G3 having a positive refractive power; a fourth lens group G4having a positive refractive power; a fifth lens group G5 having anegative refractive power; and a sixth lens group G6 having a positiverefractive power.

The first lens group G1 is constituted by, in order from the object, anegative meniscus lens L11 having a concave surface oriented toward theimage side, a biconcave lens L12, a biconcave lens L13, and a biconvexlens L14. The negative meniscus lens L11 has an aspherical surface onboth sides thereof. Moreover, the biconcave lens L12 has an asphericalobject-side surface.

The second lens group G2 is constituted by, in order from the object, abiconvex lens L21 and a cemented lens including a negative meniscus lensL22 having a concave surface oriented toward the image side and apositive meniscus lens L23 having a convex surface oriented toward theobject side.

The third lens group G3 is constituted by, in order from the object, acemented lens including a biconvex lens L31 and a negative meniscus lensL32 having a concave surface oriented toward the object side.

The fourth lens group G4 is constituted by, in order from the object, anegative meniscus lens L41 having a concave surface oriented toward theobject side and a biconvex lens L42. The biconvex lens L42 has anaspherical image-side surface.

The fifth lens group G5 is constituted by a cemented lens including, inorder from the object, a biconcave lens L51 and a positive meniscus lensL52 having a convex surface oriented toward the object side. Thepositive meniscus lens L52 has an aspherical image-side surface.

The sixth lens group G6 is constituted by, in order from the object, abiconvex lens L61, a cemented lens including a biconvex lens L62 and anegative meniscus lens L63 having a concave surface oriented toward theobject side, and a cemented lens including a biconvex lens L64 and abiconcave lens L65. The biconvex lens L62 has an aspherical object-sidesurface. The biconcave lens L65 has an aspherical image-side surface.

An aperture stop S is provided between the third lens group G3 and thefourth lens group G4, and the aperture stop S forms the fourth lensgroup G4.

Varying magnification from the wide-angle end state to the telephoto endstate is performed by moving the first lens group G1 toward the imageside and then moving the same toward the object side, moving the secondlens group G2 toward the object side, moving the third lens group G3toward the object side, moving the fourth lens group G4 toward theobject side, fixing the fifth lens group G5 in relation to the imageplane, and moving the sixth lens group G5 toward the object side suchthat the distances between the respective lens groups are changed. Theaperture stop S is moved toward the object side integrally with thefourth lens group G4.

Focusing from an object at infinity to an object at a close distance isperformed by moving the second lens group G2 toward the image side.

When image blur occurs, image blur correction (vibration reduction) onthe image plane I is performed by moving the fifth lens group G5 as thevibration-reduction lens group VR so as to have a component in thedirection orthogonal to the optical axis. In an image capturing lens inwhich the focal length of an entire system is f and a vibrationreduction coefficient (the ratio of an image moving distance on animaging plane to a moving distance of a moving lens group during blurcorrection) is K, in order to correct rotation blur of angle θ, thevibration-reduction lens group VR (a moving lens group) for image blurcorrection may be moved in the direction orthogonal to the optical axisby (f×tan θ)/K.

In Example 8, in the wide-angle end state, since the vibration reductioncoefficient is −0.93 and the focal length is 16.40 mm, the movingdistance of the vibration-reduction lens group VR for correcting therotation blur of 0.81° is −0.25 mm. In the intermediate focal lengthstate, since the vibration reduction coefficient is −1.02 and the focallength is 23.50 mm, the moving distance of the vibration-reduction lensgroup VR for correcting the rotation blur of 0.68° is −0.27 mm. In thetelephoto end state, since the vibration reduction coefficient is −1.28and the focal length is 34.00 mm, the moving distance of thevibration-reduction lens group VR for correcting the rotation blur of0.57° is −0.26 mm.

Table 8 illustrates the values of respective specifications of Example8. Surface numbers 1 to 32 in Table 8 correspond to optical surfaces ofm1 to m32 illustrated in FIG. 29 .

TABLE 8 [Lens Specification] Surface number R D nd νd *1 208.62300 3.0001.76690 46.9 *2 16.71640 11.616  1.00000 *3 −175.02069 1.700 1.7669046.9 4 110.47412 1.976 1.00000 5 −309.93761 1.700 1.49700 81.7 650.80447 1.826 1.00000 7 48.81082 5.374 1.75520 27.6 8 −305.35584 (D8) 1.00000 9 44.00730 5.080 1.64769 33.7 10 −220.95399 0.100 1.00000 1145.68721 1.000 1.84666 23.8 12 18.95011 4.835 1.60342 38.0 13 51.37666(D13) 1.00000 14 52.59784 6.421 1.49700 81.7 15 −32.17632 1.400 1.8466623.8 16 −47.86287 (D16) 1.00000 17 (Aperture stop) 3.263 1.00000 18−46.57030 1.300 1.90366 31.3 19 −281.42063 0.100 1.00000 20 109.623583.171 1.84666 23.8 *21 −72.38183 (D21) 1.00000 22 −78.11006 1.3001.80400 46.6 23 29.63097 3.221 1.80518 25.4 *24 65.36297 (D24) 1.0000025 33.81626 7.605 1.49700 81.7 26 −44.63696 0.100 1.00000 *27 86.444747.374 1.49700 81.7 28 −28.00000 1.500 1.74950 35.2 29 −250.50625 0.5001.00000 30 46.84110 6.390 1.49700 81.7 31 −60.00000 2.000 1.80610 41.0*32 122.72298 (D32) 1.00000 [Aspheric Data] Surface κ A4 A6 A8 A10 11.00000e+00 1.39337e−06 −1.56403e−09 −2.43613e−12   5.76634e−15 20.00000e+00 6.81735e−06 −4.70283e−09 9.66754e−11 −2.75609e−13 31.00000e+00 −2.75105e−06  −4.68963e−09 6.12032e−11 −2.39910e−13 211.00000e+00 2.96251e−06 −3.94707e−09 1.51980e−11 −4.38181e−14 241.00000e+00 −3.46562e−06   2.48929e−09 1.12700e−11 −3.06893e−14 271.00000e+00 1.85219e−06 −2.91274e−09 −1.43450e−11   1.77124e−14 321.00000e+00 1.48107e−05  7.00561e−09 −1.17225e−11   8.02298e−14 [VariousData] W M T f 16.40 23.50 34.00 FNo 2.84 2.84 2.89 ω 54.1 39.9 29.4 Y20.00 20.00 20.00 TL 163.819 156.784 160.573 BF 26.203 30.775 40.005[Variable Distance Data] Focusing on infinity Focusing on close point WM T W M T D0 ∞ ∞ ∞ 336.18 343.22 339.43 β — — — −0.0457 −0.0645 −0.0945f 16.40 23.50 34.00 — — — D8 22.206 10.203 2.000 23.643 11.741 3.714 D1311.561 4.934 5.407 10.123 3.396 3.693 D16 3.000 11.883 19.173 3.00011.883 19.173 D21 2.000 4.717 8.936 2.000 4.717 8.936 D24 14.997 10.4211.200 14.997 10.421 1.200 D32 26.203 30.775 40.005 26.203 30.775 40.005[Lens Group Data] Lens group Starting surface Focal distance 1st lensgroup 1 −22.37 2nd lens group 9 76.68 3rd lens group 14 62.47 4th lensgroup 17 268.42 5th lens group 22 −43.69 6th lens group 25 37.51[Conditional Expression Correspondence Values] Conditional Expression(9) f5/f4 = −0.163 Conditional Expression (10) (−f1)/f6 = 0.596Conditional Expression (11) f1/f4 = −0.083 Conditional Expression (12)A(T3.5)/A(T4.0) = 1.719 (A(T3.5) = −0.0152, A(T4.0) = −0.0089)Conditional Expression (13) f2/f3 = 1.227

It can be understood from Table 8 that the variable magnificationoptical system ZL3 according to Example 8 satisfies ConditionalExpressions (9) to (13).

FIG. 30 shows graphs illustrating various aberrations (sphericalaberration, astigmatism, distortion, magnification chromatic aberration,and lateral aberration) upon focusing on an object at infinity, of thevariable magnification optical system ZL3 according to Example 8, inwhich part (a) illustrates the wide-angle end state, part (b)illustrates the intermediate focal length state, and part (c)illustrates the telephoto end state. FIG. 31 shows graphs illustratingvarious aberrations (spherical aberration, astigmatism, distortion,magnification chromatic aberration, and lateral aberration) uponfocusing on an object at a close point, of the variable magnificationoptical system ZL3 according to Example 8, in which part (a) illustratesthe wide-angle end state, part (b) illustrates the intermediate focallength state, and part (c) illustrates the telephoto end state. FIG. 32shows graphs illustrating lateral aberration of the variablemagnification optical system ZL3 according to Example 8 when image blurcorrection is performed upon focusing on an object at infinity, in whichpart (a) illustrates the wide-angle end state, part (b) illustrates theintermediate focal length state, and part (c) illustrates the telephotoend state.

It can be understood from FIGS. 30 to 32 that the variable magnificationoptical system ZL3 according to Example 8 has a satisfactory opticalperformance such that various aberrations are satisfactorily correctedin states ranging from the wide-angle end state to the telephoto endstate and from the focusing-on-infinity state to thefocusing-on-close-point state. Moreover, it can be understood that thevariable magnification optical system ZL3 has an excellent imagingperformance upon image blur correction.

According to the above-described examples, it is possible to implement avariable magnification optical system which has a bright F-value ofapproximately F2.8 and such a wide angle of view that the half-angle ofview is approximately 50° or more, and in which various aberrations arecorrected satisfactorily.

While the present invention has been described by assigning referencesymbols to elements of the embodiment for better understanding of thepresent invention, the aspect of the present invention is not limited tothis. The following content can be appropriately employed within a rangewhere the optical performance of the variable magnification opticalsystem is not diminished.

Although the numbered examples of a six-group configuration have beenillustrated as numbered examples of the variable magnification opticalsystem ZL, the present invention is not limited to this and can beapplied to other group configurations (for example, a seven-groupconfiguration or the like). Specifically, a configuration in which alens or a lens group is added to the side closest to the object side anda configuration in which a lens or a lens group is added to the sideclosest to the image side may be employed. The first lens group G1 maybe divided into a plurality of lens groups, and the respective lensgroups may be moved along different trajectories upon varyingmagnification or one of them may be fixed. Moreover, as described above,the fourth lens group G4 may have a negative refractive power or apositive refractive power. A lens group refers to a portion having atleast one lens isolated by air space which changes upon varyingmagnification or focusing.

In the variable magnification optical system ZL, a portion of a lensgroup, an entire lens group, or a plurality of lens groups may be movedin the optical axis direction as a focusing lens group in order toperform focusing from an object at infinity to an object at a closedistance. Moreover, such a focusing lens group can be applied toautofocus and is also suitable for driving based on an autofocus motor(for example, an ultrasonic motor, a step motor, a voice coil motor, orthe like). As described above, although it is most preferable thatentire the second lens group G2 be configured as a focusing lens group,a portion of second lens group G2 may be configured as a focusing lensgroup. At least a portion of the fifth lens group G5 may be used as afocusing lens group. Moreover, although the focusing lens group mayinclude one single lens and one cemented lens described above, thenumber of lenses is not particularly limited and the focusing lens groupmay include one or more lens components.

In the variable magnification optical system ZL, an entire arbitrarylens group or a partial lens group may be moved so as to have acomponent in the direction orthogonal to the optical axis or may berotated (oscillated) in an in-plane direction including the optical axisso as to function as a vibration-reduction lens group that correctsimage blur occurring due to camera shake or the like. Particularly,although it is most preferable that the entire fifth lens group G5 beconfigured as a vibration-reduction lens group, a portion of the fifthlens group G5 may be configured as a vibration-reduction lens group.Moreover, at least a portion of the second lens group G2 or at least aportion of the third lens group G3 may be used as a vibration-reductionlens group.

In the variable magnification optical system ZL, the lens surface may beformed as a spherical surface or a flat surface and may be formed as anaspherical surface. When the lens surface is a spherical surface or aflat surface, it is possible to facilitate lens processing, assembly,and adjustment and to prevent deterioration of optical performanceresulting from errors in the processing, assembly and adjustment.Moreover, deterioration of the rendering performance is little even whenthe image plane is shifted. When the lens surface is an asphericalsurface, the aspherical surface may be an aspherical surface obtained bygrinding a glass-molded aspherical surface obtained by molding glassinto an aspherical surface, or a composite aspherical surface obtainedby forming a resin on the surface of glass into an aspherical shape.Moreover, the lens surface may be a diffraction surface and may be arefractive index distributed lens (a GRIN lens) or a plastic lens.

In the variable magnification optical system ZL, it is preferable thatthe aperture stop S be disposed in the fourth lens group G4 so as to beintegrated with the fourth lens group G4 particularly. However, theaperture stop S may be configured so as to be movable separately fromthe fourth lens group G4. In addition, the aperture stop S may bearranged in the fifth lens group G5. Moreover, the role of the aperturestop may be substituted by the frame of a lens without providing aseparate member as the aperture stop.

In the variable magnification optical system ZL, each lens surface maybe coated with an anti-reflection film which has high transmittance in awide wavelength region in order to decrease flare and ghosting andachieve satisfactory optical performance with high contrast. The type ofthe anti-reflection film may be selected appropriately. Moreover, thenumber of anti-reflection films and the position thereof may be selectedappropriately. In Examples 6, 7, and 8 described above, it is preferablethat any one of the image-side surface of the lens L11, the object-sidesurface of the lens L12, the image-side surface of the lens L12, theobject-side surface of the lens L13, the image-side surface of the lensL13, and the object-side surface of the lens L14 of the first lens groupG1 or a plurality of surfaces be coated with an anti-reflection filmwhich has high transmittance in a wavelength region.

The variable magnification ratio of the variable magnification opticalsystem ZL may be between approximately 1.5 and 2.5, for example.Moreover, the focal length (a value converted in terms of a 35-mm thickplate) in the wide-angle end state of the variable magnification opticalsystem ZL may be between approximately 15 and 20 mm, for example.Moreover, the F-value in the wide-angle end state of the variablemagnification optical system ZL may be between approximately 2.7 and3.5, for example. Moreover, the F-value in the telephoto end state ofthe variable magnification optical system ZL may be betweenapproximately 2.7 and 3.5, for example. Furthermore, when the focusingstate of the variable magnification optical system ZL changes from thewide-angle end state to the telephoto end state, the F-value may beapproximately constant (a variation is equal to or smaller than 10percent of the F-value in the telephoto end state).

EXPLANATION OF NUMERALS AND CHARACTERS

-   -   ZL (ZL1 to ZL3) Variable magnification optical system    -   G1 First lens group    -   G2 Second lens group    -   G3 Third lens group    -   G4 Fourth lens group    -   G21 21st lens group    -   G22 22nd lens group    -   G41 41st lens group    -   G42 42nd lens group    -   G5 Fifth lens group    -   G6 Sixth lens group    -   VR Vibration-reduction lens group    -   S Aperture stop    -   I Image plane    -   1 Camera (Optical apparatus)

The invention claimed is:
 1. A variable magnification optical systemconstituted by, in consecutive order from an object: a first lens grouphaving negative refractive power; a second lens group having positiverefractive power; a third lens group having negative refractive power; afourth lens group having negative refractive power; and a fifth lensgroup having positive refractive power, wherein the system performsvarying magnification by changing a distance between the first lensgroup and the second lens group, a distance between the second lensgroup and the third lens group, a distance between the third lens groupand the fourth lens group, and a distance between the fourth lens groupand the fifth lens group, one lens group among the second to fifth lensgroups is fixed along the optical axis upon varying magnification, thefirst lens group has, in order from an object side, a first negativelens, a second negative lens, a third negative lens and a positive lens,and the first lens group is moved along an optical axis upon varyingmagnification.
 2. The variable magnification optical system according toclaim 1, wherein the second lens group, the third lens group and thefourth lens group are moved toward the object side upon varyingmagnification.
 3. The variable magnification optical system according toclaim 1, wherein the first lens group is temporarily moved toward theimage side upon varying magnification from a wide-angle end state to atelephoto end state.
 4. The variable magnification optical systemaccording to claim 1, wherein each of the first negative lens and thesecond negative lens is a single lens.
 5. The variable magnificationoptical system according to claim 1, wherein the first negative lens isa meniscus lens.
 6. The variable magnification optical system accordingto claim 1, wherein the second negative lens has an aspherical surface.7. The variable magnification optical system according to claim 1,wherein the third negative lens is a biconcave lens.
 8. The variablemagnification optical system according to claim 4, wherein the firstnegative lens is a meniscus lens.
 9. The variable magnification opticalsystem according to claim 8, wherein the second negative lens has anaspherical surface.
 10. The variable magnification optical systemaccording to claim 9, wherein the third negative lens is a biconcavelens.
 11. The variable magnification optical system according to claim1, wherein the following conditional expression is satisfied:0.350<f1/f4<0.750 where f1: a focal length of the first lens group f4: afocal length of the fourth lens group.
 12. The variable magnificationoptical system according to claim 1, wherein the second lens groupconsists of five lenses.
 13. The variable magnification optical systemaccording to claim 1, wherein the third lens group consists of one lenscomponent.
 14. The variable magnification optical system according toclaim 1, wherein the fourth lens group has an aspherical lens surfaceclosest to an image.
 15. The variable magnification optical systemaccording to claim 14, wherein the following conditional expression issatisfied:1.100<A(T3.5)/A(T4.0)<5.000 where A(T3.5): an asphericity at a point onthe aspherical surface where light corresponding to F-value of 3.5passes through the aspherical surface in a telephoto end state A(T4.0):an asphericity at a point on the aspherical surface where lightcorresponding to F-value of 4.0 passes through the aspherical surface ina telephoto end state.
 16. An optical apparatus having the variablemagnification optical system of claim 1 mounted thereon.
 17. A methodfor manufacturing a variable magnification optical system, wherein thevariable magnification optical system is constituted by, in consecutiveorder from an object: a first lens group having negative refractivepower; a second lens group having positive refractive power; a thirdlens group having negative refractive power; a fourth lens group havingnegative refractive power; and a fifth lens group having positiverefractive power, the method comprising: arranging the respective lensgroups in a lens barrel such that the system performs varyingmagnification by changing a distance between the first lens group andthe second lens group, a distance between the second lens group and thethird lens group, a distance between the third lens group and the fourthlens group, and a distance between the fourth lens group and the fifthlens group, and one lens group among the second to fifth lens groups isfixed along the optical axis upon varying magnification; configuring thefirst lens group to have, in order from an object side, a first negativelens, a second negative lens, a third negative lens and a positive lens;and arranging the first lens group to be moved along an optical axisupon varying magnification.